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Aiming at the influence on the suspension control accuracy caused by the suspension windings rotor induced current of a squirrel-cage bearingless induction motor (SBIM), a novel three-speed wound bearingless induction motor (WBIM) is designed based on establishing the stator-rotor equivalent circuit, deriving the exciting current-suspension slip ratio equation and analyzing the magnetic field distribution with odd pole pairs and dipole pairs. The stator is embedded with a fixed 4 pole winding and a 2/6 pole changing winding, while the rotor is wound with series-parallel windings connecting at a slip ratio ring. By changing the connection method of the stator coils and adjusting the three-phase voltage source, and controlling the short circuit of the rotor winding central point, it can realize that the rotor can only induce the torque winding magnetic field under three speeds. Through the finite element analysis (FEA), the induced current, air gap magnetic density, suspension force and electromagnetic torque of the traditional SBIM and the new WBIM are quantitatively calculated and compared. Finally, an experimental platform is built for further verification.

Considering the influence of iron core saturation and complex boundary conditions, a novel no-load magnetic field analytical method and system multi-objective optimization model for interior permanent magnet synchronous motor (IPMSM) are proposed. Firstly, an analytical method based on magnetic potential permeance method is proposed. The complex cogging effect and equivalent air gap permeability function are fully considered in this method. Furthermore, on the basis of Taguchi optimization design based on Fuzzy theory, an improved optimization model considering multi-variable interaction is proposed. Among them, in order to comprehensively consider the performance of electromagnetic, vibration, and temperature rise, five optimization objectives including torque, pulsation, cogging torque, loss, and flux density have been optimized. The sensitivity of design variables and the interaction between variables are not ignored. Finally, a 6-pole 36-slot IPMSM is manufactured for prototype experiments. A large number of prototype experiments, finite element, and computational fluid dynamics simulation analysis including no-load magnetic field, back electromotive force, temperature rise, electromagnetic torque, and so on are carried out. The accuracy and rationality of the proposed no-load magnetic field analysis method and global optimization model have been well verified.

Servo press has become the future development trend in the field of the forging equipment. Its core component is servo motor (permanent magnet synchronous motor, PMSM), and serve press is completely driven and controlled by the servo motor. For the ideal drive and transmission system of the advanced servo press, a conventional PMSM cannot do this well, so an integrated PMSM must be used. This article focuses on the integration of servo motor, facing the application background of the servo press, and proposes a novel hollow two-sided output PMSM integrated with mechanical planetary gear. The novel integrated PMSM is designed based on a conventional PMSM. The integrated design is described in detail. The two prototypes of a conventional PMSM and an integrated PMSM are developed and two prototypes are studied experimentally. The experimental results show that the novel integrated PMSM has good electrical properties and it can well match the moment of inertia between the load and the motor. The rapid response (related to the square of the gear ratio), stability (related to the gear ratio), and the output torque (related to the gear ratio) of the novel integrated PMSM are superior to the conventional PMSM. In addition, the application of the novel integrated PMSM can make the whole structure of the servo press more compact, more efficient, and can realize mechanical synchronization.

Vehicle wheel traction forces play an important role in vehicle performance, especially for four-wheel-drive vehicles, where a transfer case clutch is used to distribute torque between front and rear wheels. Due to lack of production ready low-cost torque sensor, the transfer case clutch torque is not measured and needs to be estimated accurately to optimize vehicle traction performance. This article proposes to estimate the transfer case clutch torque by forming an estimation problem with unknown system input(s). Specifically, a unified clutch torque estimation model is developed for different clutch conditions, where overtaken-clutch case is treated as a special case of slip-clutch condition with slip-speed equals to zero. Note that under overtaken condition, the associated system model with only one known input is different from that under slip condition with two known inputs. A real-time implementable recursive solution for unknown input(s) is obtained by utilizing an unknown input observer based on the extended Kalman filter (EKF-UIO) algorithm. Comparing with the existing direct estimation method and experimental measured data, it is found that the proposed EKF-UIO algorithm is able to reduce both absolute mean square error and relative-mean-square error significantly with respect to the measured clutch torque under both slip and overtaken conditions. In summary, the EKF-UIO estimation algorithm based on the unified clutch torque model is able to estimate clutch torque accurately.

The complicated rate-dependent hysteresis due to the input current and rotation speed of the magnetorheological clutch (MRC) greatly hinders its applications in robotics. In this article, it is first proved that the Preisach model is a special diagonal recurrent neural network (dRNN) with a binary step activation function. Motivated by this, the condition and the internal knowledge of the classical dRNN in modeling the rate-dependent hysteresis are investigated and validated. To guarantee that such a condition holds in dRNN training, a new loss function is proposed. The coupled rate-dependent hysteresis of an MRC prototype is, then, precisely modeled by the dRNN with the current input and speed input. By employing the trained dRNN model, the MRC torque is controlled using the feedforward scheme with no external torque sensors. Taking the advantage of being free-of-parameter tuning for the classical inverse multiplicative structure control (IMSC), a dRNN-based IMSC is proposed by finding the best feasible neuron and solving a nonlinear function. Various experiments validate much better control accuracy and higher bandwidth of the IMSC over the model-based proportional–integral–derivative control.

Due to the increasing demand for high-speed motors with high stability, bearingless motors have attracted much attention. Bearingless permanent magnet synchronous motors (BPMSMs) are a kind of motor, which uses suspension force to eliminate the motor bearings. This article proposes a five-phase BPMSM with 10 slots and 8 poles. Based on the principle of suspension force of BPMSM, an analytical expression of the suspension force is derived for the proposed BPMSM. To improve the suspension stability and torque, an optimization method consisting of a response surface model and a multiobjective optimization algorithm is employed. Not only the geometric parameters but also the winding distribution are considered in the optimization process. Finally, the effectiveness and superiority of the optimal design are verified by experiment.

Robot force-controlled task executions require an accurate perception of the contact force/torque. When a six-axis force/torque (F/T) sensor is attached to the robot wrist, the compensation precision is affected by many non-contact features, such as the end-effector gravity, inertial, centrifugal, Coriolis forces, and the mechanical errors of the sensor. However, it is complicated to identify all parameters at the same time. Some features will be ignored in practice applications, e.g., surface finishing, human-robot interaction, and haptic applications. In this paper, a novel end-effector gravity compensation method for the F/T sensor is proposed, which identifies the end-effector gravity, its center, and the biases (the rotation between the sensor and robot, the robot installation declination, the bias of sensor). Our key is the rotation calibration while the transformation between the F/T sensor and robot is unknown. Simulation and experimental results show that the proposed method works effectively. In a wrist-mounted F/T sensor system, compared to the previous limited method, the compensation error in common force control channel Fz by our method diminishes 1.0% of the end-effector gravity (i.e., 21.7% relative improvement).

An increasing interest for permanent magnet synchronous machines with low torque ripple and low vibration is observed. The purpose of this paper is to investigate the topology of non-uniformly distributed teeth and its influence of on cogging torque, tooth ripple harmonics and torque ripple of permanent magnet synchronous machines. The topologies with different number of non-uniformly distributed teeth are investigated. Analytical procedure is developed to illustrate the impacts of non-uniformly distributed teeth on cogging torque and unbalanced magnetic pull (UMP), and then identify the appropriate non-uniformly distributed teeth. A commercial 10kW 8-pole 48-slot V-shaped IPM machine is taken as the reference base machine. The machines with 2- and 6 non-uniformly distributed teeth are chosen to make an overall comparison to that with the well-known skewing slots. The machine with 2 non-uniformly distributed teeth is finally chosen to be fabricated. Intensive experiments including cogging torque, back-EMF, load current, efficiency and instantaneous torque are done.

In this paper, a method of simultaneous sensorless rotor position and torque estimation is proposed for interior permanent magnet synchronous machines at standstill and low speed. The proposed method estimates the torque using high frequency inductances identified from the current variations due to high frequency square wave voltage injections in the estimated dq-axeswhich are simultaneously used for sensorless rotor position estimation. The proposed method is not dependent on the fundamental model and has taken the cross-coupling effect into consideration, allowing for low cost and fast torque estimation at standstill and low speed. Both simulations and experiments are carried out to verify the effectiveness of the proposed method.

Many controllers are available in the market for controlling the Permanent Magnet Synchronous Motor (PMSM) drive application, though the most preferably used one is Proportional Integral (PI), controller. However, it is found that the PI and other latest controllers have their own merits and demerits while analyzing their outputs via comparison. Thus it is decided to test the deed of hybrid controllers that can serve a lot better than standalone controllers for precise control applications. In this article, a conventional PI controller has been applied in closed-loop system in combination with recent controllers like Proportional Resonant Controller (PRC), Fractional order Proportional Integral Derivative (FOPID), Hysteresis Current Controller (HCC) and Fuzzy Logic Controller (FLC). The resultant hybrid controllers were (i) PI-FOPID (ii) PI-FLC (iii) FOPID-FLC (iv) HCC-FLC and (v) PRC-FLC. All these hybrid controllers are designed using MATLAB platform and the speed and torque responses are compared to allocate the better performance award to the hybrid controllers. The continuous and intermittent loads are considered while registering time-domain response of PMSM-Pump application. With the aid of time-domain response and THD, the topology to be tested in prototype is chosen and tested for resemblance of the speed response with the simulation output. PI-FLC hybrid controller tends to render optimum performance characteristics among all the other hybrid controllers and the same is validated in real time through hardware results.

Wound rotor induction motors (WRIM) are widely used in a vast number of high output power industrial applications due to their capability of reaching high start torques while maintaining low inrush currents. Nonetheless, these machines are very prone to require early maintenance, and the possibility of presenting rotor winding asymmetry failures is high due to their more complex rotor circuit. Although some recent works have proposed techniques that overcome the drawbacks of conventional methods, an additional research effort for the development of alternative approaches able to enhance their performance and reliability is desirable. In this work, a new method for the diagnosis of rotor asymmetries in WRIM is presented. The proposed methodology is based on a feed-forward neural network (FFNN) feed by suitable fault severity indicators, which rely on the maximum energy density of higher order harmonics (amplified by the failure) at strategic regions of the time-frequency maps obtained from stray flux signals under startup transient. Experimental results for three different levels of rotor asymmetries in a 11 KW WRIM prove the reliability of the enhanced proposed system in comparison to conventional approaches that only rely on the main sideband fault-harmonic amplitudes.

This paper proposes an intensive study for common-mode voltage (CMV) elimination/reduction in a five-level dual T-type multilevel converter (5LDT-MLC) drive. An advanced and fast model predictive control (MPC) approach is developed for CMV reduction (CMVR) and CMV elimination (CMVE) based on preselection of the switching states (SS). In addition, the proposed approach considers the torque control and the capacitor balancing of the proposed drive as essential aspects of MLC drives. A detailed study for the impact of the converter SS on the CMV is presented. The main features of the proposed MPC approach are reducing the complexity of the cost-function, the tuning burden of the weighting factors, and the computation time by more than 80% compared to conventional MPC techniques. A hardware implementation based on Silicon Carbide (SiC) T-type MLC is built. The experimental results demonstrate the effectiveness of the proposed MPC approach to mitigate/eliminate the CMV along with achieving the torque command and balancing the DC link capacitors. Unlike conventional CMVR techniques, the proposed approach reduces the CMV by 75% of its normal values without jeopardizing the harmonic contents, drive efficiency, and flux as well as torque ripples.

We address the motion planning problem for a robotic system whose configuration manifold contains a group of rotations. Our approach is applied to a free-floating space robot composed of a three-dimensional base (a spacecraft) and an anthropomorphic onboard manipulator. The robot is actuated by the torques exerted at the joints of the onboard manipulator. A coordinate-free representation of rotations is utilized. The Lagrangian formalism is employed in order to derive a dynamics model of the robot that takes the form of a control system defined on the group of rotations and the joint space of the onboard manipulator. Using the conservation of angular momentum of the robot, a Jacobian motion planning algorithm is designed relying on the Endogenous Configuration Space Approach. The performance of the algorithm is verified by computer simulations.

This paper has proposed a novel design of dual PM vernier machine with T-shape consequent pole rotor. The analytical model of T-shape magnet rotor based on differential magnetic network method are firstly derived. Given the additional optimizing parameter, edge arc difference, T-shape consequent pole (TCP) rotor has the potential to produce 6% higher fundamental airgap flux density or 30% higher PM utilization ratio than regular fan-shape consequent pole rotor. The influence of magnet size parameters including magnet thickness, pole pitch ratio and arc difference angle on airgap flux density of TCP rotor is then analyzed. The torque performance of TCP in regular consequent pole and dual PM consequent pole vernier machines are also studied. The comparison shows that T-shape consequent pole can produce higher torque than fan-shape magnet in vernier machines. At last, a prototype of dual-PM vernier machine with TCP rotor is built and tested, which has achieved 28 Nm/L measured torque density.

A generalized fault-tolerant control (FTC) strategy for the field-oriented control (FOC) and direct torque control (DTC) of five-phase fault-tolerant permanent magnet (FPFTPM) motors under various open-circuit faults is presented in this paper. Most previous studies regarding FTC target a specific primary control algorithm and involve different reduced-order transformation matrices and additional current controllers, which increase the complexity of the entire drive system. In this study, a solution to the aforementioned problems is devised by developing optimal fault-tolerant voltages, which are derived from fault-tolerant mechanism analysis and steady-healthy design. Because the coordinate transformation need not be changed and additional voltage compensation is not required, a minimal control drive system reconfiguration under various open-circuit faults can be achieved to avoid accommodating the change of the primary control algorithm. The proposed control strategy not only improves the torque performance and dynamic response under healthy and fault conditions but also adapts to both FOC and DTC. Experimental results for a 2 kW FPFTPM motor prototype are provided to evaluate the proposed strategy.

Parallel compliances can be very efficient in modifying robots' natural dynamics provided that, compliance force profiles match the required joint forces. To contribute to this area, firstly by presenting the optimality condition of a parallel compliance for energy efficiency, we show that a conventional compliance does not fulfill this condition in general because its force profile is invariant with respect to its movement direction. To overcome this, we secondly introduce the concept of "unidirectional compliance" which produces torque in only one movement direction of a reciprocating joint. Furthermore, we propose a method to implement a desired unidirectional compliance profile. Thirdly, we theoretically show that there exists a combination of unidirectional and conventional compliances to produce two arbitrary torque profiles for moving back and forth in a reciprocating task. Fourthly, we propose a framework to find and design a suitable combination of unidirectional and conventional compliances in mono- and bi-articular configurations for increasing the energy efficiency of an n-DoF serial manipulator. Also, theoretical supports for the presented method are developed. Finally, we demonstrate the applicability of the proposed approach as well as its efficacy in energy consumption reduction in a set of simulations and experiments.

Human-machine shared control has become an effective cutting-edge approach to enhance driving safety and assist in the transition from manual to autonomous driving. However, driving authority allocation when conflict occurs between a human driver and a machine still represents an intractable problem. In order to solve this problem, this paper proposes an adaptive steering torque coupling framework to achieve the human-machine shared control with conflict resolution. Additionally, a driver trajectory prediction method considering human-machine interaction is established based on the extended state observer and long short-term memory network. In addition, the human-machine shared steering system is modeled based on a non-cooperative dynamic game by the prediction model method for path-tracking, and the obtained solution is given according to the Nash equilibrium. Particularly, a dynamic load allocation approach is designed to resolve human-machine conflict and relax the driver. In order to verify the strategy formed based on the proposed framework, a driver-in-the-loop experiment is conducted. The experimental results reveal that the proposed strategy can effectively reduce the human-machine conflict torque and ensure a driver has absolute control authority. Furthermore, the proposed strategy can also transfer the driving workload between the driver and machine, provide driving experience, or improve driving comfort when there is no conflict.

Multiphase machines with a prime number of phases (five and seven) have shown better torque density than machines with other phase numbers. Unfortunately, these machines require a special stator design. Hence, this paper proposes general rewinding techniques to obtain a five-phase winding from the existing standard three-phase stator frames. The proposed rewinding techniques are applied to construct a five-phase star-connected synchronous reluctance machine (SynRM 1) and a novel combined star-pentagon winding (SynRM 2). Simple mathematical formulations are introduced to compute the equivalent winding factor. The performance of five-phase SynRMs is analyzed using 2D Ansys Maxwell transient simulations under the same copper volume for both healthy and faulty cases. SynRM 1 and 2 provide 6.56% and 13.35% higher torque compared to the three-phase SynRM at rated current and at optimal current angle. The torque ripple is decreased by 17% and 30% respectively. Moreover, SynRM 1 and 2 offer a better performance at the faulty case; e.g. at one phase opened, the average torque of SynRM 1 and 2 is 82% and 108% higher compared to the three-phase SynRM. In addition, the torque ripple is reduced by about 63% and 81%. Finally, experimental results are done to validate the proposed winding techniques.

Predictive Current Control (PCC) is an emerging technique offering advantages like easy inclusion of multi-variable objectives, non-linear constraints and excellent dynamic performance. In the conventional PCC (CPCC), the computational complexity is increased with the increase in the number of voltage vectors (VV). As the control action gets updated in every control interval, the deployment of fast-processors with large data-handling capability is inevitable, which limits the real-time application of PCC scheme. Further, applying a single VV for the complete sample period causes an increase in the ripples in torque and flux under steady-state operation. This paper introduces a duty-modulated PCC scheme with low complexity for the PMSM drive, to address the above limitations. The proposed scheme utilizes only three VVs in every sample interval, unlike the CPCC, where seven VVs are employed. This yields a reduction in the number of computations without forfeiting the drive performance. Subsequently, an effective duty modulation scheme is employed to improve the performance of PMSM drive under steady-state, where the application of active and zero VV aid to minimize the flux and torque ripples. In order to affirm the effectiveness of the proposed scheme, comprehensive comparisons are performed with the CPCC and recent literature.

Efforts to improve the drive performance of classical model predictive torque control (MPTC) for induction motors (IM) have continued for decades. Existing methods often suffer from the intensive computations, poor robustness and limited quality. To resolve these problems, this manuscript proposes an efficient MPTC for IM with flexible duty ratio optimization. In the proposed strategy, candidate voltage vectors are restricted to be in a subset of area enclosed by voltage limit hexagon, where all the possible two-vector combinations and part of three-vector combinations are included. To quickly determine the optimal input voltage, a tailored duty ratio optimization algorithm based on voltage error minimization is designed. Experiments clearly indicate the proposed strategy can effectively improve the steady performance with respect to classic MPTC and some other typical methods. More importantly, the proposed strategy can be conveniently extended by increasing the number of three-vector combinations to achieve steady performance close to space vector modulation based direct torque control (SVM-DTC). It is inspiring to see faster dynamic response together with less torque ripple than SVM-DTC is provided during a large transient due to the rigorously enhanced optimality of input voltage. Finally, the robustness of proposed scheme is experimentally validated.

Automotive applications demand high efficiency, good reliability, and a wide operating speed range within limited DC bus voltage constraints. In this paper, a zero degree displacement dual three-phase PMSM is derived from an original 3-phase PMSM to enhance the power rating as well as the operating speed range. The proposed topology can be used as an alternative to the conventional configuration of three-phase PMSM with a bidirectional DC-DC converter for electric vehicles. Even though the commonly used dual three-phase PMSM with split-phase winding eliminates the sixth harmonic torque pulsation, a large circulating current is generated during six-step operation, which results in additional stator copper loss. In this paper, six-step operation of the symmetric dual three-phase PMSM with zero degree winding displacement is proposed to achieve maximum inverter utilisation. Both harmonic circulating current and torque pulsation were observed to be within satisfactory levels using this configuration. A changeover algorithm is also proposed to enable a smooth transition between closed-loop current vector control during low and medium speed operation to open-loop six-step voltage angle control for high speed operation. The performance of the proposed method is experimentally validated on a 3kW dual three-phase PMSM drive.

A simplified universal fault-tolerant direct torque control (FTDTC) strategy of five-phase fault-tolerant permanent magnet (FPFTPM) motors under various open-circuit faults is presented in this paper. In the proposed FTDTC strategy, the fault-tolerant currents are derived from the fault-tolerant mechanism analysis and steady-healthy design. The problems of existing FTDTC strategies that need to change coordinate transformation and add extra voltage compensation can be overcome. Thus, the minimal control drive system reconfiguration under different faults can be realized in the real sense. Especially, the steady-healthy controller is designed to suppress the torque ripples and achieve the high-quality torque given even under fault operation conditions; then, it is not necessary to set a special voltage vector or add a PI controller. Furthermore, the FTDTC strategy is improved to be realized under the dq coordinate system based on the flux adaption. Hence, the reduced d-axis current under different operating conditions, including fault conditions, can be ensured. This FTDTC strategy without any control reconfiguration is proposed under the premise of ensuring good performance during both healthy and fault operations. Finally, the simulation and experimental results for a FPFTPM prototype are offered to verify the feasibility of the proposed strategy.

This paper deals with the LUT-less sensorless control of synchronous reluctance (SyR) machines at zero and low speed, where LUT-less stands for avoiding the use of flux-map look-up tables (LUTs) or other pre-determined machine parameters. The new signal-injection based control scheme called the Locus of Incremental Saliency ratio Tracking (LIST) is presented, where a pulsating high-frequency voltage component is used for position tracking and a second rotating signal-injection is dedicated to on-line estimating the incremental saliency ratio. A trajectory of constant incremental saliency ratio is used for torque regulation, resulting in stable control at all operating conditions, including overload. This despite the effect of cross-saturation, which is known to introduce position error and harm the control stability progressively with the load. The proposed scheme is validated experimentally on a 1.1 kW SyR machine test-bench. Alternative LUT-less torque control laws are investigated, and their stability limits put in evidence using convergence analysis and experiments.

This study presents a computationally efficient model predictive torque control (MPTC) method for permanent magnet synchronous machines (PMSMs). The existing MPTC methods require solving complex optimization problems in iterations; this approach is computationally demanding. In contrast, the proposed MPTC transforms the optimization problem into two subproblems and derives the corresponding solutions explicitly using numerical techniques, which entail linearization of the torque function and current constraint; the proposed approach can significantly reduce the computational burden. Additionally, the proposed MPTC does not involve any control gains and weighting factors; hence, gain tuning is not required for the proposed MPTC. These features are advantageous when implementing torque control. Using a 4-kW PMSM drive, the effectiveness of the proposed MPTC is demonstrated both numerically and experimentally in terms of dynamic performance and computational efficiency. This is realized by comparing the proposed method with the existing methods.

Due to the double layer airgap configuration, the even-order harmonic components exist in the phase back electromotive force (EMF) of flux-modulation electrically-excitation double-stator synchronous machine (FMEE-DSM), thus resulting in relatively high torque ripples. To promptly and effectively suppress these torque ripples, this paper proposes and implements a second-order iterative learning control (ILC) strategy to minimize the main harmonic torque components based on the periodically repetitive characteristic of torque ripples in the FMEE-DSM. Via harmonic analysis on the torque ripples caused by the cogging torque and the non-sinusoidal induced EMFs, the dominative harmonic component, namely, the 7th order component, can be precisely identified and then involved in the proposed ILC for torque ripple suppression. To verify the feasibility of proposed control strategy, a test bench of the FMEE-DSM control system was built based on dSPACE 1103. Accordingly, both the static and dynamic performances of the FMEE-DSM were investigated under the conditions of no-load and rated load. The theoretical analysis, computer simulation and hardware experimentation are given to verify the proposed second-order ILC.

The mode transition process (MTP) from electric mode to hybrid electric mode (EM-to-HM) will cause the deterioration in occupant comfort of PHEV, to tickle this issue, a torsional oscillation-considered mode transition coordinated control strategy and a novel general evaluation index for MTP are developed in this research, the quality of mode transition and transient torsional oscillation of gears (TTOGs) during MTP are taken into consideration comprehensively. An action dependent heuristic dynamic programming algorithm which takes the vehicle jerk, friction loss and TTOGs as evaluation index is used to optimize the pressure curve of clutch oil and the compensation torque of motor in the entire EM-to-HM process. Finally, the simulation results and hardware-in-the-loop tests show that vehicle jerk and TTOGs are suppressed, and the driving comfort can be improved accordingly.

In high power traction drives using induction motors, during operation above the base speed, it is generally preferred to drive the machine in the square-wave mode since it offers maximum DC-bus utilization and reduced switching loss. However, the conventional field oriented control method cannot control the drive effectively in square-wave mode since independent control of torque and flux is difficult to achieve due to stator voltage saturation. This paper proposes a new technique to control the drive in the square-wave mode where only one degree of freedom is available for control. In the square-wave mode, the proposed method controls the torque of the machine by directly varying the stator voltage angle with respect to the rotor flux axis. The flux of the machine is kept at a required value below the saturation limit by appropriate selection of the operating point. The proposed control strategy also offers good torque dynamics in the square wave operating mode. The control algorithm is experimentally verified on a 5.5 kW induction machine drive and the experimental results are presented.

This article proposes a novel gain-scheduling control method to improve vehicle lateral stability based on a variable-parameter-dependent approach. A time-varying velocity-dependent model to describe the vehicle lateral dynamic characteristics is constructed under cornering stiffness uncertainties and controller saturation. A novel Lyapunov function with variable-parameter-dependent Lyapunov matrix is established to develop the conditions. Using the proposed Lyapunov function, a general condition of the variable-parameter-dependent saturated robust yaw moment controller is provided in terms of time-varying parameter-dependent matrix inequalities. In order to obtain a tractable solution, a condition is further developed with finite linear matrix inequalities. Moreover, an optimal distribution method is adopted to generate the desired yaw moment based on torque allocation. These torques are computed by optimizing the distribution errors and tire workloads. Simulations results under both J-turn and double-lane changing scenarios are used to illustrate the merits of the proposed method. The control synthesis approach is also applicable to other applications involving time-varying parameters.

Model predictive current control (MPCC) is commonly used method for the control of permanent magnet synchronous motor (PMSM) drive. MPCC is simple to implement and faster to execute on digital platform. The classical cost function in MPCC does not contain any weighting factor thereby resulting in a simpler cost function for the selection of optimal voltage space vector (VSV). Conventional MPCC applied to PMSM results in higher torque ripples. The ripples in the torque and stator-flux can be reduced by reducing the duration of application of active VSV. This article proposes an MPCC based on virtual voltage space vector (VVSV) for reducing the torque ripples and improve the THD in stator-current without affecting dynamic performance. Duty ratio for VVSV is chosen proportional to commanded speed to reduce change in stator-current thereby reducing ripple in torque stator-flux. The VVSVs have magnitude near to developed back-EMF space vector. Proposed MPCC is compared with conventional MPCC and two other MPCC based on VVSV. Effectiveness of proposed MPCC is successfully verified after comparing the results of experimentation at different speed and load conditions. Proposed MPCC fails to reduce ripple in torque and stator-flux above base speed and proposed scheme collapses into conventional MPCC.

Cable-driven parallel robots (CDPRs) are more convenient to use in large-scale applications than rigid-link robots due to the advantages such as simple structure, high load capacity, and low inertia of cables. However, using cables to drive an end-effector comes with the low equivalent stiffness issue in out-of-plane direction for the CDPRs planar configuration, which causes long-lasting and high amplitude out-of-plane vibrations under an external disturbance. This study presents a novel method to suppress the out-of-plane vibrations without distorting in-plane positioning control simultaneously for planar CDPRs. The proposed method provides the ease of using only the cable tensioning forces instead of an additional actuator to control the out-of-plane vibrations by decoupling the in-plane and out-of-plane dynamics. The switching stiffness control method is used for out-of-plane vibration control, while a classical control method (PID) is used for in-plane dynamics control. These two control inputs are then coupled by a bias torque variation in a torque distribution algorithm. The effectiveness of the proposed method is presented both in simulations and experimental results. The experiments are performed for the specified in-plane positions and an in-plane trajectory tracking study when the planar CDPR excited to out-of-plane vibration in the normal direction. The out-of-plane vibration suppression time is considerably reduced compared to the free-vibration case, and any distortion on the in-plane positioning control is not observed.

Dual three-phase permanent magnet synchronous motors (DTP-PMSMs) feature a satisfactory capability of the fault-tolerant operation due to the inherent multiphase configuration. To improve the control performance of the DTP-PMSMs under the open-phase fault, accurate inductances are critical. This paper presents an extended Kalman Filter (EKF) based inductance estimation strategy for DTP-PMSMs with one phase opened. Firstly, the multi-synchronous-rotating frame (MSRF) based DTP-PMSMs modeling under the single open-phase fault is presented. Secondly, the system space-state model and proposed EKF based estimation algorithm considering inverter nonlinearity are presented. Finally, the inductance estimation is performed by experiments under both steady and transient states. The estimation results have been verified by torque measurements which confirm the validity of the proposed method.

An adaptive wheel-legged shape reconfigurable mobile robot, based on a scissor-like mechanism, is proposed for an obstacle detecting and surmounting robot, moving on complex terrain. The robot can dynamically adjust its own shape, according to the environment, realizing a transformation of wheel shape into leg shape and vice versa. Each wheel-legged mechanism has one degree of freedom, which means that only the relative motion of the inner and outer discs is needed to achieve the transformation of the shape into a wheel or a leg. First, the force analysis of the conversion process of the wheel-legged mechanism is carried out, while the relationship between the driving torque and the friction factor in the non-conversion trigger stage and in the conversion trigger stage is obtained. The results showed that the shape conversion can be better realized by increasing the friction factor of the trigger point. Next, the kinematics analysis of the robot, including climbing the obstacles, stairs and gully, is carried out. The motion of the spokes tip is obtained, in order to derive the folding ratio and the surmountable obstacle height of the wheel-legged mechanism. The parameters of the wheel-legged structure are optimized, to obtain better stability and obstacle climbing ability. Finally, a dynamic simulation model is established by ADAMS, to verify the obstacle climbing performance and gait rationality of the robot, in addition to a prototype experiment. The results showed that the surmountable obstacle height of the robot is about 3.05 times the spoke radius. The robot has the stability of a traditional wheel mechanism and the obstacle surmount performance of a leg mechanism, making it more suitable for field reconnaissance and exploration missions.

Lumbar spine injuries caused by repetitive lifting rank as the most prevalent workplace injury in the United States. While these injuries are caused by both symmetric and asymmetric lifting, asymmetric is often more damaging. Many back devices do not address asymmetry, so we present a new system called the Asymmetric Back Exosuit (ABX). The ABX addresses this important gap through unique design geometry and active cable-driven actuation. The suit allows the user to move in a wide range of lumbar trajectories while the “X” pattern cable routing allows variable assistance application for these trajectories. We also conducted a biomechanical analysis in OpenSim to map assistive cable force to effective lumbar torque assistance for a given trajectory, allowing for intuitive controller design in the lumbar joint space over the complex kinematic chain for varying lifting techniques. Human subject experiments illustrated that the ABX reduced lumbar erector spinae muscle activation during symmetric and asymmetric lifting by an average of 37.8% and 16.0%, respectively, compared to lifting without the exosuit. This result indicates the potential for our device to reduce lumbar injury risk.

The main challenges for Finite Set-model Predictive Torque and Flux Control (MPTC) include huge calculation amount, large torque ripple, and the selection of weighting factor. To deal with these challenges and achieve the fastest torque response, a novel MPTC strategy with virtual voltage vector-based pattern is proposed in this paper. In each control period, a desired voltage vector is computed based on the maximum torque variation rate. The virtual desired voltage vector is combined by using basic voltage vectors with the minimum switching times. The switching pattern between two adjacent control periods is optimized by using a cost function in realtime. Compared with the traditional MPTC approach, the novel strategy has multifaceted improved performances: faster torque response, less calculation amount, lower switching frequency, reduced torque ripple, higher efficiency and no weighting factor. The proposed method is contrasted with traditional MPTC method and a well-known generalized multiple-vector-based MPC method via experiments.

This paper presents the design and control of a new Halbach-array-based two-phase motor (HTM) with a 3-D printed coil mount and magnet housing for precision motion control applications. The motor is based on a 2-pole Halbach cylinder that generates a uniform magnetic field within its inner diameter. Each pole has 10 magnet segments. This uniform field simplifies the Lorentz force calculation based on the volume integration. In addition, it allows for the real-time measurement of the rotor position based on Hall-effect sensors. Compared with conventional stepper motors and iron-core DC motors, this motor design can produce a continuous torque and precise positioning at any angular position without a cogging torque. In this paper the design of the motor together with its dynamics and control are presented. The design uses only one type of square-cross-section magnets that are readily available, making it easy to scale the design to a variety of sizes and torque capabilities. The 3-D printed stator and rotor housings allow for the motor to be constructed at a low cost in a short time. With a total magnet volume of only 30.7 cm3, a total effective coil volume of only 10.4 cm3, and a maximum current of 4 A, the maximum torque generated is 0.044 Nm. Experimental results with closed-loop control on a simple empirically-identified plant model are provided to validate the magnetic design of the motor. The feedback signals are from two Hall-effect sensors connected to a microcontroller, offering a theoretical angular resolution of 0.16. A minimum step size of 0.32 is demonstrated in positioning with closed-loop control. The motor has the capacity to track the commanded motion and speed with an error less than 0.64.

For interior permanent magnet synchronous motor (IPMSM) drives, accurate torque control and loss-minimizing operation are essential issues to keep up the excellent features of IPMSM. However, flux linkage variations owing to various operating conditions make it challenging to maintain their efficiency at the highest level during overall operating conditions. In this paper, a real-time torque control is proposed to satisfy both torque control accuracy and high-efficiency operation in consideration of flux linkage variations. Firstly, torque control under the minimum copper-loss is modeled as a constrained optimization problem to satisfy both torque reference tracking and loss-minimizing operation in both maximum torque per ampere (MTPA) and flux-weakening regions. Current references are calculated through robust numerical and region identification algorithms in a command optimizer. Moreover, both stator flux linkages and dynamic inductances are estimated to reflect the flux variations in real-time, which is the parts of a parameter estimator. The proposed estimators are designed to extract fundamental flux linkages and their variations while maintaining high dynamic performance. The performance of the proposed methods is verified by simulation and experimental results where premade look-up tables are not utilized at all.

Pole-phase modulation based multiphase induction motor (PPMIM) drives possess the capability of providing an extended range of speed-torque for high power traction application with the available additional degrees of freedom in the multiphase machine. As observed in previous open-loop results of PPMIM drives presented in the literature, the transient currents often exceed twice the rated currents. To address this issue, this paper focuses on the modelling and advanced control of the PPMIM drives during all possible pole-phase combinations. The dynamic mathematical modelling of the PPMIM in actual phase variable domain is presented in detail. Since this model involves time-dependent inductances and torque, the machine model equations are transformed into dq domain using transformation matrices. The transformation matrices, modelling equations in the arbitrary reference frame and multiphase inverter are modelled by considering all parameters of possible pole-phase combinations. Based on the proposed modelling equations, an indirect field oriented control (IFOC) is implemented for PPMIM drives for smoother operation in all possible modes of operation. The modelling equations, as well as IFOC of PPMIM drive, are implemented in MATLAB to illustrate the behaviour of machine during transients as well as different load torques. The proposed concepts are also validated on laboratory setup and the hardware results are demonstrating the smoother transition as well as steady state operation of PPMIM drive in pole changeovers as well as both pole-phase combinations.

Voltage induced in the DC winding by the armature field in wound field switched flux (WFSF) machines will induce voltage perturbation in the voltage supply and cause DC winding current ripple and field excitation fluctuation. This will challenge the DC voltage controller and deteriorate the control performance, especially when the load and / or the rotor speed are high. In this paper, the dual 3-phase armature winding design with a phase shift of 30 electrical degrees is employed in the partitioned stator WFSF machines to reduce the on-load DC winding induced voltage. Analytical deductions and finite element (FE) results demonstrate that the dominant six-order induced voltage harmonic can be suppressed to zero. Hence, the peak-to-peak induced voltage in the 12/11- and 12/13-pole partitioned stator WFSF machines can be reduced by 83.35% and 82.53%, respectively. Due to the improvement of winding factors, the torque densities are 4.85% and 5.60% higher, respectively. Prototypes are built and tested to verify the analytical and FE results.

It is known that permanent magnet vernier machine has multiple flux field harmonics which can produce stable torque. However, some flux field harmonics would create torque that undermines the torque output. Such as the 6slots26poles split-tooth PMVM here, of which modulated flux field outputs torque while fundamental flux field undermines torque output. In this paper, a 26poles PMVM with coding-shaped tooth is proposed. The coding-shaped tooth can introduce permeance harmonics with specific phase and amplitude, thus modulating flux fields that all output torque. Air-gap permeance harmonics of the proposed and the regular split-tooth PMVM are obtained via FEA. Based on MMF-permeance model, flux fields of two machines and their contributions to average torque are investigated, proving that the proposed machine has multiple flux fields that all output torque. By optimizing geometry of coding-shaped tooth, the proposed machine obtains largest average torque and smallest torque ripple simultaneously. Electromagnetic performances of the optimized machines are studied in semi-analytical way and FEA. It is proved that with same overall size, PM usage and copper loss, the proposed machine achieves 30% larger torque density, 86% smaller cogging torque and 62% lower torque ripple than its counterpart. Finally, a 16Nm (rated)prototype is built and tested.

A modified configuration for Permanent Magnet Assisted Synchronous Reluctance Motors (PMaSyRM) is studied in this paper. Conventionally, the PM materials are inserted in the flux barriers region of the rotor. Consequently, the PMs sizing parameters will be restricted to the available space that may limit the efficient use of PMs benefits. In this study, a portion of the rotor structure is replaced with an Interior PM (IPM) rotor so that an axially segmented integration of IPM and SyRM is obtained. Thus, the PMs design is performed specifically in the IPM segment independent of the SyRM scheme, while the SyRM segment remains PM-less. The main motivation of this concept is to improve the contribution of the PM material in the total torque as well as utilizing the special property of the proposed rotor configuration for pulsating torque reduction. A computationally cost-effective algorithm is proposed for the optimal design of IPM-SyRM motor by which a low-power design is carried out for a lightweight electric vehicle. The results for torque profile characteristics, PM volume, power-factor, and efficiency are compared with a conventional PMaSyRM that has been optimally designed as the reference case. Finally, a prototype is constructed to verify the theoretical analysis.

In this paper, a new design of the state observer is proposed to reduce the unstable low-speed region of the adaptive full-order observer (AFO) based speed sensorless speed control of induction motors (IM). The proposed state observer is designed in z-domain rather than in s-domain following the pole-placement approach. The convergence rate of the proposed observer can be made faster than that of the IM poles without extra oscillation effects and the unstable low-speed region of AFO can be reduced to the zero-synchronous-frequency (ZSF) line. Also, a modified adaptation law of the AFO is derived to estimate the rotor speed. Based on the modified AFO, a continuous control set model predictive control (CCS-MPC) is designed for the inner-loop torque control. The cost function of the CCS-MPC is made of the predicted tracking errors on the state and control input. Finally, the dual-loop speed sensorless speed control using the modified AFO and CCS-MPC is presented in simulations and experiments.

In this article, the fault-tolerant control (FTC) strategy based on current redistribution is compared for three types of triple redundant 3×3-phase motor: surface-mounted permanent magnet synchronous motor (SPMSM), synchronous reluctance motor (SynRM), and permanent magnet assisted synchronous reluctance motor (PMa-SynRM), under a single-phase open-circuit fault. The output torque of SPMSM and SynRM is produced by permanent magnet (PM) torque and reluctance torque, respectively. Nevertheless, for PMa-SynRM, it is necessary to determine the distribution ratio of PM torque and reluctance torque in the proposed FTC strategy. By comparing the FTC performance of motors, the conclusions are as follows: (1) Torque ripple of the SPMSM can be completely suppressed. (2) Torque ripple minimization for the SynRM and PMa-SynRM can be realized. (3) Optimal solution obtained in SynRM can also be applied to the PMa-SynRM when the load is heavy. In addition, to reduce the complexity and improve the reliability of the control system, a mono-inverter driven triple paralleled control system is constructed in healthy and postfault operations. The comparison results of the FTC strategy for three types of motor are obtained by simulation. And the experimental results based on a 3×3-phase PMa-SynRM are accomplished to verify the feasibility of the theory.

This paper proposes a torque ripple reduction method based on speed ripples for PMSM drives. The torque ripples are first estimated based on speed harmonics at low speed. Based on that, the optimal harmonic current reference is then derived to fully compensate the estimated torque ripple with minimum stator resistive loss. An extended state observer (ESO) based deadbeat harmonic current controller (DHCC) is also presented in the rotor reference frame (RRF) to inject the optimal harmonic currents with good performance in steady state and transients. To extract the harmonic currents for harmonic current control and speed harmonics for torque ripple estimation with fast convergence and good accuracy, an adaptive linear neural (ADALINE) network-based filter is implemented in this paper. Simulations and experiments are carried out to show the validity and performance of the proposed torque ripple reduction method.

A dual-flexible manipulator with a telescopic arm is affected by joint flexibility, load flexibility, and bearing friction, which will cause angular velocity fluctuation. Besides, the motion of the telescopic arm leads to dynamic parameters of the flexible load in the servo system time-varying. The variation of dynamic parameters increases fluctuations of angular velocity. Fluctuations in angular velocity will aggravate the vibration of the manipulator and affect the control accuracy of end-effectors. In this paper, the adaptive PI control strategy with the disturbance observer (DOB) suppresses the vibration of the manipulator by weakening the angular velocity fluctuations. Firstly, dynamics equations of the dual-flexible manipulator servo system considering the bearing friction are established by using the assumed mode method. Next, the low-pass filter in DOB is designed according to the robust stability theorem, so that the servo system can satisfy the stability under dynamic parameters time-varying and friction torque simultaneously. Then, the adaptive law and the over-load compensation control law are designed by Lyapunov’s stability theorem. Finally, numerical simulation analysis and control experiments of the manipulator are carried out. The simulation and experimental results show that: 1) The bearing friction torque can cause angular velocity fluctuations, but the DOB can effectively reduce the influence of the disturbance torque. 2) The adaptive control strategy can effectively reduce angular velocity errors under conditions that the telescopic arm is in different lengths. Therefore, the adaptive PI control strategy with the DOB can effectively suppress angular velocity fluctuations of the manipulator.

In this paper, a novel model predictive torque control (MPTC) method for switched reluctance machines (SRM) is proposed based on the equivalent linear SRM model and the improved switching table. Firstly, an improved switching table with only 6 switching states is developed based on the inductance characteristics. The adoption of this improved switching table not only reduces the computational burden by 25% but also improves the torque control performance and system efficiency at high-speed region. However, the look-up-table (LUT) based MPTC methods suffer from occupying numerous storage space. To ease this issue, the simple linear SRM model is utilized. The flux-linkage and torque equivalent transformations are introduced to address the difference between the linear and nonlinear SRM models. With these transformations, the MPTC realized on the linear SRM model is proposed. Compared to 1530 storage units consumption to store 3 2-dimensional (2-D) LUTs in the LUT-based MPTC methods, the proposed method only occupies 228 storage units. Experimental results on an 8/6 SRM setup verify that the proposed method effectively eliminates the commutation torque ripple with lower execution time, less storage space, and improves torque control performance at a high-speed range compared with the conventional LUT-based method.

The high precision control of angular speed in low-speed gimbal servo systems is an essential topic in the operation of the single gimbal control moment gyro (SGCMG). This paper proposes a discrete control algorithm to suppress the influence of various disturbances on the low-speed gimbal servo system and the constraint between controller parameters and sampling time is established to ensure the stability of the system. To begin with, the disturbance analysis of the low-speed gimbal servo system is presented, including the torque ripple in the permanent magnet synchronous motor (PMSM), nonlinear friction, coupling torque caused by the spacecraft motion, and the parameter uncertainties. Then, a composite control method combining the sliding mode controller (SMC) with sliding mode observer (SMO) is applied to the speed loop and q-axis current loop. The interferences are estimated by two sliding mode observers while sliding mode controllers are designed to eliminate the influence brought by the residual disturbances. The stability of the overall system is proved based on the Lyapunov criterion. Finally, simulation and experimental results verify the effectiveness of the proposed composite control method.