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Previous studies on the stability analysis of haptic devices have predominantly focused on single-DOF devices, thereby limiting attention to multi-DOF devices, particularly those employing multi-rate sampling schemes. In this paper, we introduce a formulation for the coupled dynamics between the haptic device and the virtual environment for a multi-DOF haptic device controlled using a dual-rate sampling scheme. Subsequently, we analyze its stability through the application of a dynamic decoupling strategy within an exact discrete-time state-space framework while the device is engaged in rendering a virtual wall along one of its operational space coordinates. Furthermore, we explore how the combined influence of the dual-rate sampling approach, time delay, and the mechanical design affects the stability boundaries of the multi-DOF haptic device at a fixed workspace location as well as within the entire usable workspace. Additionally, we utilize a model-order reduction (MOR) framework to simplify the determination of the device's stability limits, irrespective of the specific combinations of time delay and sampling rates employed. [ABSTRACT FROM AUTHOR]

Current research on the interference of GNSS (Global Navigation Satellite System) array antennas focuses on the single interference effect and the improvement of interference hardware capability, while the multi-degree-of-freedom (DOF) interference model and mechanism remain to be fully studied. Aiming at this problem, this paper analyzes the preconditions for the definition of anti-jamming degrees of freedom and the characteristics of super-DOF interference through formula derivation and simulation. First, by analyzing the influence of the number of interfering signals on the angular resolution, the prerequisite of the definition of anti-interference degrees of freedom in the airspace is proposed. Second, the definition of anti-interference degrees of freedom is used to calculate the change rule of the critical power of the interference under different numbers of interfering signals. Finally, the influence of super-DOF interference on the array antenna is analyzed. The results show that the prerequisite for the anti-interference freedom of the array antenna is that the distribution interval of the interfering signal is greater than 15°, taking a four-array element uniform circular array antenna as an example. The critical interference power of the array antenna decreases by about 15 dB when the number of interfering signals exceeds the degrees of freedom of the array antenna's interference immunity, provided that the interference resolution is satisfied. The conclusions of this paper give the critical power change rule of multi-DOF interference and the effect of super-DOF interference, as well as the prerequisites for the setting of interference signals, which can be used, for example, in the deployment of distributed interference sources and the development of anti-jamming algorithms. [ABSTRACT FROM AUTHOR]

With the aim of recovery and training of the patients suffering from osteoarthritis, muscular dystrophy and stroke, we present a design and validation model of a mechanical rehabilitation device for the hand. The objective is to bring together the advances in mechanism effectiveness, reduced size, simpler assembly, and lower manufacturing costs. As a result, the proposed exoskeleton employs a minimal number of components and has a very simplistic design. Moreover, training on the designed hand should reduce spasticity, paresis and recover the tone of the muscle. The designed device can deliver motions that include opening/closing, pronation/supination of the hand and flexion/extension of the hand as well as the arm. This work will focus toward increasing DOF, cost-effectiveness and some modifications in the design to ease assembly. Three servo motors and a linear actuator were used virtually to obtain four different motions. 3D designing of the parts, parts assembly, simulation and studies like kinematic, dynamic and static were carried out. Static analysis of the device shows the device is able to carry the loads without any fracture or deformation. Preliminary results obtained through motion curves show this device is able to deliver all the required motions smoothly without facing any dead point. Design and validation model of a mechanical rehabilitation device for the hand. Advances in mechanism effectiveness, simpler assembly, and lower manufacturing costs. Study focuses towards increasing DOF, cost-effectiveness and ease assembly. [ABSTRACT FROM AUTHOR]

Current research on the interference of GNSS (Global Navigation Satellite System) array antennas focuses on the single interference effect and the improvement of interference hardware capability, while the multi-degree-of-freedom (DOF) interference model and mechanism remain to be fully studied. Aiming at this problem, this paper analyzes the preconditions for the definition of anti-jamming degrees of freedom and the characteristics of super-DOF interference through formula derivation and simulation. First, by analyzing the influence of the number of interfering signals on the angular resolution, the prerequisite of the definition of anti-interference degrees of freedom in the airspace is proposed. Second, the definition of anti-interference degrees of freedom is used to calculate the change rule of the critical power of the interference under different numbers of interfering signals. Finally, the influence of super-DOF interference on the array antenna is analyzed. The results show that the prerequisite for the anti-interference freedom of the array antenna is that the distribution interval of the interfering signal is greater than 15°, taking a four-array element uniform circular array antenna as an example. The critical interference power of the array antenna decreases by about 15 dB when the number of interfering signals exceeds the degrees of freedom of the array antenna’s interference immunity, provided that the interference resolution is satisfied. The conclusions of this paper give the critical power change rule of multi-DOF interference and the effect of super-DOF interference, as well as the prerequisites for the setting of interference signals, which can be used, for example, in the deployment of distributed interference sources and the development of anti-jamming algorithms.

In order to address the self-collision problem associated with the operation of modern industrial robots, this paper proposes a multi-degree-of-freedom collision detection algorithm that can detect self-collision in single arm and double arm robots as well as collision with the load. Firstly, the zero pose of the Denavitiâˆ'Hartenberg model is built based on the manipulator configuration, and the coordinate information of each key point is obtained through a rotation and translation operation of the matrix. Then, the positional relation and distance between the detected objects are determined by the spatial geometry theory, and finally, collision is detected using a collision matrix. By simulating two groups of single arms and two groups of double arms, and from the laboratory testing of SR10C in the SIASUN robot factory, it has been verified that the proposed algorithm has good collision detection capability. Without the use of sensors, cameras, and other external devices, the collision between the arm and the load, and the collision between the cooperative robot and the load may be effectively detected and mitigated. [ABSTRACT FROM AUTHOR]

The steering mirrors and the focusing mechanisms are the key components of the optical system. Traditional steering mirrors driven by voice coil actuator or piezoelectric stack actuator have the disadvantages of short stroke, self-locking difficulty and poor structural reliability. These defects limit the performance of the steering mirrors and make it difficult to be compatible with the focusing mechanism. As a result, additional focusing devices are required in the optical system, which significantly increases the complexity of the system. To simplify the optical system, a large stroke three-degree-of-freedom (3-DOF) piezoelectric steering mirror (PSM) which can realize both light path adjustment and focus adjustment is proposed in this study. Two rotational degrees of freedom of the PSM are used to adjust the light path, and a translational degree of freedom is used to adjust the focus. The screwed-typed piezoelectric actuators (STPAs) are designed to drive the PSM by exciting the travelling wave. The feasibility of the operating principle and reliability of the proposed PSM have been verified by finite element simulation. A prototype of the PSM is fabricated and tested. The experimental results show that the PSM achieves rotational degrees of freedom around the x -axis, y -axis and translational degree of freedom along the z -axis with maximum ranges of ±0.17 rad, ±0.17 rad, and ±10 mm, respectively, meeting the application requirements of the optical systems. The resolutions of the two rotary motions of the PSM are 28 μrad, and 21 μrad, respectively, and that of the translational motion is 0.5 μm. Finally, the position adjustment and focusing operations of the image are demonstrated to validate the potential application of PSM in optical systems. [Display omitted] • A large-stroke high-precision fast-response screwed-typed piezoelectric actuator (STPA) is designed in this study. • A novel 3-DOF piezoelectric steering mirror is proposed to realize the light path adjustment and focusing functions. • The proposed PSM is verified to adjust the image position adjustment and focus adjustment. [ABSTRACT FROM AUTHOR]

Stick-slip piezoelectric actuators are widely used in precision engineering due to their high accuracy and small size. However, most of these actuators achieve multi-DOF motion by serially connecting multiple units, resulting in a non-compact structure and large assembly errors. To resolve this issue, this paper proposes a spherical actuator consists of a rotor and four drive units distributed around the rotor. Each drive unit comprises a piezoelectric shear stack and a piezoelectric plate. By utilizing the cooperation of piezoelectric elements, various driving modes with different performance and control complexity can be switched. To understand the influence of position and orientation of the drive units on the actuator's performance, a dynamic model describing the behavior of the proposed actuator is established. This model takes into account the behavior of the drive units, friction and motion transmission between the drive units and the rotor, as well as transformation of coordinates. Finally, a prototype is developed based on the design, and the three-DOF motion performance of the prototype is tested under different drive modes. This work contributes to the mechanical design of multi-DOF precision positioning devices and the study of motion modes. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ultra-low frequency vibration isolation system is proposed to protect precision devices. • Diaphragm bellow isolators and electromagnetic actuators are adopted in the system. • Auxiliary isolators of variable stiffness are used to adapt operation and transportation. • A broadband control law based on the actuation-measurement state decoupling is proposed. • The effectiveness of the proposed vibration isolation system is verified by experiments. High precision devices are sensitive to low frequency background vibration. In order to meet the requirement of vibration isolation and adaptation to different working modes, a multi-DOF (Degree-of-Freedom) ultra-low frequency vibration isolation system is proposed. The system uses diaphragm bellow isolators to bear static load and electromagnetic actuators to exert control forces. Auxiliary isolators of variable stiffness are used to make the system adaptive to operation and transportation. The dynamic model of the vibration isolation system is established to analyze vibration characteristics and investigate control laws. A broadband control law based on the actuation-measurement state decoupling is proposed and the mixed feedback and feedforward control is adopted to realize ultra-low frequency vibration isolation. Numerical and experimental results have demonstrated that the proposed system is able to isolate ground vibration effectively. The initial vibration isolation frequency is reduced to 0.5 Hz and the transmissibility reaches −8.3 dB at 1 Hz and −21.9 dB at 2 Hz. [ABSTRACT FROM AUTHOR]

This study proposed a multiple degree-of-freedom (DoF) continuous wrist angle estimation approach based on an electrical impedance tomography (EIT) interface. The interface can inspect the spatial information of deep muscles with a soft elastic fabric sensing band, extending the measurement scope of the existing muscle-signal-based sensors. The designed estimation algorithm first extracted the mutual correlation of the EIT regions with a kernel function, and second used a regularization procedure to select the optimal coefficients. We evaluated the method with different features and regression models on 12 healthy subjects when they performed six basic wrist joint motions. The average root-mean-square error of the 3-DoF estimation task was 7.62°, and the average R2 was 0.92. The results are comparable to state-of-the-art with sEMG signals in multi-DoF tasks. Future endeavors will be paid in this new direction to get more promising results.

This study proposed a multiple degree-of-freedom (DoF) continuous wrist angle estimation approach based on an electrical impedance tomography (EIT) interface. The interface can inspect the spatial information of deep muscles with a soft elastic fabric sensing band, extending the measurement scope of the existing muscle-signal-based sensors. The designed estimation algorithm first extracted the mutual correlation of the EIT regions with a kernel function, and second used a regularization procedure to select the optimal coefficients. We evaluated the method with different features and regression models on 12 healthy subjects when they performed six basic wrist joint motions. The average root-mean-square error of the 3-DoF estimation task was 7.62°, and the average R 2 was 0.92. The results are comparable to state-of-the-art with sEMG signals in multi-DoF tasks. Future endeavors will be paid in this new direction to get more promising results. [ABSTRACT FROM AUTHOR]

Currently, additive manufacturing (AM) technology has received significant attention from both academia and industry. AM is characterized by fabricating geometrically complex components in a layer-by-layer manner, and greatly reduces the geometric complexity restrictions compared with traditional manufacturing. As AM is no longer limited to the normal three degrees of freedom (DOF) (three-axis) systems, there are many new multi-DOF AM machines been developed with various aims. It is, therefore, necessary that a review of the topic with regard to multi-DOF AM is performed for future AM system development. This paper, focuses on reviewing publications related to multi-DOF AM according to the number of DOF on an AM machine. The major part of the paper aims to inspire both researchers and engineers to further develop and improve multi-DOF AM systems to achieve different goals. The final part of the paper discusses the findings together with future research directions. [ABSTRACT FROM AUTHOR]

Dielectric elastomers (DEs) consist of highly compliant electrostatic transducers which can be operated as actuators, by converting an applied high voltage into motion, and as sensors, since capacitive changes can be related to displacement information. Due to large achievable deformation (on the order of 100%) and high flexibility, DEs appear as highly suitable for the design of soft robotic systems. An important requirement for robotic systems is the possibility of generating a multi degree-of-freedom (MDOF) actuation. By means of DE technology, a controllable motion along several directions can be made possible by combining different membrane actuators in protagonist-antagonist configurations, as well as by designing electrode patterns which allow independent activation of different sections of a single membrane. However, despite several concepts of DE soft robots have been presented in the recent literature, up to date there is still a lack of systematic studies targeted at optimizing the design of the system. To properly understand how different parameters influence the complex motion of DE soft robots, this paper presents an experimental study on how geometry scaling affects the performance of a specific MDOF actuator configuration. The system under investigation consists of two cone DE membranes rigidly connected along the outer diameter, and pre-compressed out-of-plane against each other via a rigid spacer. The electrodes of both membranes are partitioned in four sections that can be activated separately, thus allowing the desired MDOF actuation feature. Different prototypes are assembled and tested to study the influence of the inner radius as well as the length of the rigid spacer on the achievable motion range. For the first experimental study presented here, we focus our analysis on a single actuation variable, i.e., the rotation of the rigid spacer about a fixed axis. A physics-based model is then developed and validated based on the collected experimental measurements. A model-based investigation is subsequently performed, with the aim of studying the influence of the regarded parameters on the rotation angle. Finally, based on the results of the performed study, a model-based optimization of the prototype geometry is performed.

Multi-degree-of-freedom (multi-DOF) piezoelectric motion stage is an important part of modern manufacturing industry. In order to perform high precision outputs in a large travel range, various multi-DOF piezoelectric motion stages have been proposed and applied for decades. This paper is concentrated on reviewing the research on a piezoelectric motion stage. It involves the major components, operating principles of different actuation modes, design schemes, and structures of the multi-DOF piezoelectric motion stages. In this paper, the summary and classification of the actuation modes used in the multi-DOF piezoelectric motion stages are presented, mainly including the resonance actuation mode, inertial actuation mode, clamping and feeding actuation mode, and direct actuation mode; the multi-DOF piezoelectric motion stage is divided into multi-actuator type and single-actuator type according to the number of actuators used in the motion stage, in which the multi-actuator type includes series, parallel, and series-parallel types from the viewpoint of structure mechanism; in addition, the output performances of the stages are compared, and the state of the arts of the stages are discussed and summarized; the further efforts and future research perspectives are highlighted.

Low-frequency vibration energy harvesting is a promising technology for providing floating buoys and small marine robots with sustainable energy from ocean waves. A spherical vibration energy harvester with multiple degrees of freedom has the advantages of good multi-directional adaptability and compact structure. However, its magnetic field distribution in three-dimension space is much more complex due to the combined effect of a series of cylindrical permanent magnets mounted on the surface of a gimbaled pendulum. The traditional finite element method is too time-consuming to perform efficient parameter design and optimization. To solve this problem, this work develops an analytical electromagnetic model for the spherical vibration energy harvester based on Biot-Savart Law. This model can be used to predict spatial magnetic flux distribution and electromotive force for given magnet and coil parameters. The accuracy and computational cost of the analytical model is verified by the comparison with the finite element method. Furthermore, the optimization of electromagnetic parameters is implemented to achieve maximum energy conversion efficiency. Finally, an optimized prototype is fabricated and tested in both laboratory and real sea. The resonant frequency and energy conversion efficiency of the prototype reaches 1.0 Hz and 25.45 %, respectively. It is shown that the experimental results are in good accordance with the analytical results. [Display omitted] • This work develops an analytical electromagnetic model for spherical energy harvester. • Configuration and electromagnetic parameters of energy harvester are optimized. • Linearized method is used to evaluate output power and energy conversion efficiency. • An optimized prototype is fabricated and tested in both laboratory and real sea. • Maximum output power of prototype reaches 105 mW in sea trial with low sea state. [ABSTRACT FROM AUTHOR]

This paper presents the electromagnetic analysis of a novel fluid damping based hybrid drive multi-degrees-of-freedom permanent magnet motor based on analytical and 3D finite element methods. The spatial magnetic field calculation model, torque analysis model, oil film model and electromagnetic-thermal coupling are presented and developed. Based on the simulation calculation results, some important features on the magnetic field and torque characteristics, oil film and electromagnetic-thermal coupling are derived and their effects are discussed in detail with some further improvement design possibilities. The results provide the primary theoretical guide for the configuration design, optimization and control research of three degrees of freedom deflection type actuators.

Highlights • A general design routine for multi-DOF TMD is proposed. • The multi-DOF TMD is designed via the graphical approach. • Frequencies of the TMD are formulated analytically. • A three-DOF TMD is implemented for damping single mode. Abstract The multi-degree-of-freedom (MDOF) tuned mass damper (TMD) has demonstrated a more effective performance than single-DOF and multiple SDOF TMDs. For a damping mass in the space, there are maximum six DOFs; however, only along the vibration direction of the main structure can the motion of the TMD be utilized to control the vibration mode. Therefore, the maximum available DOFs of a TMD for mitigating single translational mode are three (i.e. one translational DOF and two rotational DOFs). A general routine of suppressing single vibration mode by multi-DOF TMD is presented, especially, a three-DOF TMD is used for example. Based on the non-dimensional dynamic model, the design parameters of the TMD are optimized via the simulated annealing algorithm according to the H∞ criterion. The graphical approach is utilized to design the configuration of the TMD with prescribed DOFs. Stiffness and natural frequencies are formulated analytically by the compliance matrix method, based on which the dimensions of the TMD are determined. It is demonstrated that the SDOF and two-DOF TMDs are special cases of the three-DOF TMD from the point of mathematical modeling, numerical optimization and design methodology. Theoretical formulation is verified by conducting hammer tests on the TMD under various geometry configurations. After employing the three-DOF TMD, 86.5% reduction of the amplitude of the frequency response function (FRF) of an I-shaped part is achieved, which shows 29.5% improvement than previous two-DOF TMD. [ABSTRACT FROM AUTHOR]

This paper presents the problem of tracking the generated reference trajectory by the simulation model of a multi-DOF robot arm. The kinematic transformation between task space and joint configuration coordinates is nonlinear and configuration dependent. To obtain the solution of the forward kinematics problem, the homogeneous transformation matrix is used. A solution to the inverse kinematics is a vector of joint configuration coordinates calculated using of pseudoinverse Jacobian technique. These coordinates correspond to a set of task space coordinates. The algorithm is presented which uses iterative solution and is simplified by considering stepper motors in robot arm joints. The reference trajectory in Cartesian coordinate system is generated on-line by the signal generator previously developed in MS Excel. Dynamic Data Exchange communication protocol allows sharing data with Matlab-Simulink. These data represent the reference tracking trajectory of the end effector. Matlab-Simulink software is used to calculate the representative joint rotations. The proposed algorithm is demonstrated experimentally on the model of 7-DOF robot arm system.

• The interaction between waves and a multi-DOF cylindrical buoy was analyzed. • Independent PTO damping was applied to each DOF via the custom development, and six motions were considered. • The buoy under pitch-surge motion is not advisable due to the increase of 101.6 % in bottom pressure compared to the initial pressure in still water. • Coupled motion can lead to a less intense wave field distribution than a single motion and reduce the risk of overtopping. • The heave damping has a significant effect on both the maximum wave run-up and load. With the development of wave energy converters (WECs), multi-degree-of-freedom (multi-DOF) buoy has become popular. The effect of nonlinear phenomena, such as wave run-up and wave impact, on an oscillating buoy WEC, may decrease its efficiency and even lead to overturning, plastic deformation, and fatigue failure. This study used a Fortran code for the custom development of Flow-3D software to apply independent power take-off (PTO) damping to each DOF. A hydrodynamic simulation model of the interaction between a wave and cylindrical buoy under six types of motions was developed and verified through model tests of the motion response of the buoy and wave run-up on it. Wave run-up heights and maximum wave loads on buoys with different motions and PTO combinations were investigated and compared. The numerical results show that coupled motion can lead to a less intense wave field distribution than a single motion and reduce the risk of overtopping. In addition, the bottom pressure of the buoy for the pitch–surge motion increased by a maximum of 101.6 % compared to the initial pressure. For independent linear PTO damping, heave damping has the most significant influence on the maximum wave load on the coupled motion buoys, followed by surge damping, while pitch damping has no significant effect. The results of this study can guide the designing of safe and reliable multi-DOF buoy WECs. [ABSTRACT FROM AUTHOR]

This paper presents a new concept and design of a multidegree-of-freedom (DOF) motion platform capable of controlling three DOFs rotation and three DOFs translation to provide unlimited rotational range of motion for virtual reality (VR) based on spherical wheels. Multi-DOF motion platforms have been developed for various applications such as motion simulators and game industry. In addition, motion recognition is one of main features for VR with visual display. However, existing motion platforms have critical limits of range of motion in motion realization due to mechanical linkages and their actuating mechanisms. In addition, unnatural motion control causes mismatch in the VR environment. The motion platform developed in this paper can provide six DOFs motion, and in particular, unlimited range of rotation without motion singularity. The design is compact and lightweight offering fast speed of response. Kinematic and dynamic analysis of the platform are investigated to provide a basis of motion control in an open loop. Performance of motion control is demonstrated in real scale size (ride on platform). The experimental results show that the platform is successfully capable of multi-DOF motion control and can be utilized for various applications in future demands. [ABSTRACT FROM PUBLISHER]

A new type of multiple-degree-of-freedom (multi-DOF) ultrasonic motor was developed aiming at high output torque and compact structure. To reach this purpose, a ring type composite stator was proposed with four driving feet uniformly arranged in the inner circumference of the ring stator. The stator employs two orthogonal axial bending modes and a radial bending mode, by exciting two of them simultaneously, to generate elliptic trajectories on driving feet tips and to push sphere rotor around x , y and z axis respectively. Based on the deduced criteria, a specific combination of the A(0, 5) axial bending modes and R(0, 2) radial bending mode were chosen to realize that the rotating directions of the elliptical driving trajectories on four feet tips can push the sphere rotor to spin in the same direction consistently, thus the efficiency and output performance will be improved by decreasing the slip between feet and rotor. FEM was used to design the motor including selecting key parameters to tune the resonant frequencies by sensitivity analysis, and a prototype was fabricated and tested. The experiment results showed that the maximum output torque of the motor is 0.118 N m and the maximum speed is 55 r/min. [ABSTRACT FROM AUTHOR]

This paper reports a novel four degree-of-freedom (DOF) MEMS vibratory gyroscope. A MEMS gyroscope array is then presented using the novel gyroscope unit. In the design of the proposed 4-DOF MEMS vibratory gyroscope, the elements of the drive-mode are set inside the whole gyroscope architecture, and the elements of sense-mode are set around the drive-mode, which thus makes it possible to combine several gyroscope units into a gyroscope array through sense-modes of all the units. The complete 2-DOF vibratory structure is utilized in both the drive-mode and sense-mode of the gyroscope unit, thereby providing the desired bandwidth and inherent robustness. The gyroscope array combines several gyroscope units by using the unique detection mass, which will increase the gain of sense-mode and improve the sensitivity of the system. The simulation results demonstrate that, compared to a single gyroscope unit, the gain of gyroscope array (n = 6) is increased by about 8 dB; a 3 dB bandwidth of 100 Hz in sense-mode and 190 Hz in drive-mode are also provided. The bandwidths of both modes are highly matched with each other, providing a bandwidth of 100 Hz for the entire system, thus illustrating that it could satisfy the requirements in practical applications.

This paper presents the design and analysis of a multi degree of freedom (DOF) electro-thermally actuated non-resonant MEMS gyroscope with a 3-DOF drive mode and 1-DOF sense mode system. The 3-DOF drive mode system consists of three masses coupled together using suspension beams. The 1-DOF system consists of a single mass whose motion is decoupled from the drive mode using a decoupling frame. The gyroscope is designed to be operated in the flat region between the first two resonant peaks in drive mode, thus minimizing the effect of environmental and fabrication process variations on device performance. The high gain in the flat operational region is achieved by tuning the suspension beams stiffness. A detailed analytical model, considering the dynamics of both the electro-thermal actuator and multi-mass system, is developed. A parametric optimization is carried out, considering the microfabrication process constraints of the Metal Multi-User MEMS Processes (MetalMUMPs), to achieve high gain. The stiffness of suspension beams is optimized such that the sense mode resonant frequency lies in the flat region between the first two resonant peaks in the drive mode. The results acquired through the developed analytical model are verified with the help of 3D finite element method (FEM)-based simulations. The first three resonant frequencies in the drive mode are designed to be 2.51 kHz, 3.68 kHz, and 5.77 kHz, respectively. The sense mode resonant frequency is designed to be 3.13 kHz. At an actuation voltage of 0.2 V, the dynamically amplified drive mode gain in the sense mass is obtained to be 18.6 µm. With this gain, a capacitive change of 28.11 f F and 862.13 f F is achieved corresponding to the sense mode amplitude of 0.15 μ m and 4.5 μ m at atmospheric air pressure and in a vacuum, respectively.

This paper presents the electromagnetic system design and analysis of a novel three-degrees-of-freedom deflection type permanent magnet actuator based on analytical and 3D finite element methods. The spatial magnetic field calculation model, torque analysis model and mainly the analytical formula applications are presented and developed. Based on the simulation calculation results, some important features on the magnetic field and torque characteristics are derived and their effects are discussed in detail with some further improvement design possibilities. The experiment and calculation results provide the primary theoretical guide for the configuration design, optimization and control research of three degrees of freedom deflection type actuators. [ABSTRACT FROM AUTHOR]

This paper presents a new method for the optimal synthesis of planar compliant parallel mechanisms (CPMs). The compliant limbs of CPMs are regarded as separate design domains of topology optimization problem. The finite element analysis (FEA) and matrix methods are combined to analyze the CPMs' Jacobian and stiffness matrices, based on which a new formulation is proposed for the topology optimization of multiple degree-of-freedom (DOF) compliant mechanisms. Without beginning with a known rigid-body mechanism, the proposed method finds the optimal topology of CPMs within the given design domains. The ability of the proposed method to find the optimal topology with complex kinematic behavior is demonstrated by several numerical examples and experimental study. [ABSTRACT FROM AUTHOR]

These days a Two-wheel inverted pendulum (TWIP) robot attracts public attention as it is an efficient ergonomics and easy to operate by nuance personals. Furthermore it has attractive design features like compact in size and zero turning radius. However, the traditional TWIP robots have to change its posture to reach the desired speedup and deceleration by changing the robot posture forward and backward make it difficult to control its motion process. Thus, this paper presents here the Mamdami fuzzy control logic to overcome the motion control of Multi-DOF TWIP robot and make its motion smooth and steady control. By introducing two additional DOFs the slider and the swinging configuration, the robot can maintain its vertical posture even climbing and descending on slopes. To validate the robustness of the proposed method, classic PID controller is introduced for comparison in simulations and experiments. The simulation results demonstrate the effectiveness of the system design and the better performance in robustness over classic PID control strategy. Finally, the control scheme is implemented on the practical self-designed hardware. [ABSTRACT FROM AUTHOR]

This paper mainly presents an orientation detection methodology and corresponding system for developing platform of interface and ARM single chip unit to measure the magnetic field of the irregular shaped permanent magnet of multi- DOF motor. The data acquisition and data processing are implemented by two means -- traditional Gauss meter measuring method and automated test system. Then the results by the two methods are compared to verify the availability of presented automated test system consequently. Experiment results show that this test system can detect the rotor's orientation effectively and provide useful references for further research. [ABSTRACT FROM AUTHOR]

This paper presents a novel multi-degree-of-freedom (multi-DOF) micromachined vibratory gyroscope design operated at atmospheric pressure. In this design, the complete 2-DOF vibratory structure is utilized in drive-mode and sense-mode and also, the 2-DOF sense-mode is implemented in both driving frame and proof frame, which form the double 2-DOF sense-modes. The 2-DOF vibratory structure could provide drive-mode and sense-mode with large bandwidth and the double 2-DOF sense-modes could provide high gain of gyroscope system, which improves the inherent robustness and sensitivity simultaneously. The simulation results demonstrate that the summed signal of drive-mode dynamic response is consistent with that of sense-mode and that the gain of proposed multi-DOF micromachined vibratory gyroscope can reach up to −10 dB, increased by above 8 dB compared to the design with single 2-DOF sense-mode. Meanwhile, the 3 dB bandwidth of gyroscope system is larger than 200 Hz. [ABSTRACT FROM AUTHOR]

Based on brief introduction of the operation principle and superior performance of the permanent-magnet (PM) deflection type three-degrees-of-freedom motors, one novel PM motor air-gap magnetic-field calculation schemes based on the analytical and finite-element methods are presented and scalar magnetic-flux density calculation formulae in the spherical coordinate are developed. A rotor magnetic-field model is built in a 3D finite-element software and computed with simulation to derive the flux-density distribution under different magnetization modes. The results obtained with these two methods are compared and validated. The theoretical analysis and computation results demonstrate the effectiveness of the designed structure; it is easy for the rotor to achieve a three-degree-of-freedom deflection motion, which provides references for further research and experimental design of the related motors or actuators. [ABSTRACT FROM AUTHOR]

We propose a camera actuating system using a spherical ultrasonic motor for inspection of the inside wall of a small pipe. The spherical ultrasonic motor has advantages that include three degrees of freedom, high responsiveness and high accuracy all within a compact body. We describe here the development of an outer rotor spherical ultrasonic motor (OR-SUSM) that enables a camera to rotate by more than 360° along the side of the pipe. All components, including the OR-SUSM, the sensing system, and the electric circuits, are designed to be assembled in the pipe inspection device with outer diameter of 52 mm. To control the system, the phase difference and frequency of the applied voltages are used. The rotational direction is determined by the phase difference and the angular velocity is controlled by the frequency. The completed system can be controlled to within 2° in an experimental pipe inspection test. [ABSTRACT FROM PUBLISHER]

This paper reports a novel four degree-of-freedom (DOF) MEMS vibratory gyroscope. A MEMS gyroscope array is then presented using the novel gyroscope unit. In the design of the proposed 4-DOF MEMS vibratory gyroscope, the elements of the drive-mode are set inside the whole gyroscope architecture, and the elements of sense-mode are set around the drive-mode, which thus makes it possible to combine several gyroscope units into a gyroscope array through sense-modes of all the units. The complete 2-DOF vibratory structure is utilized in both the drive-mode and sense-mode of the gyroscope unit, thereby providing the desired bandwidth and inherent robustness. The gyroscope array combines several gyroscope units by using the unique detection mass, which will increase the gain of sense-mode and improve the sensitivity of the system. The simulation results demonstrate that, compared to a single gyroscope unit, the gain of gyroscope array (n = 6) is increased by about 8 dB; a 3 dB bandwidth of 100 Hz in sense-mode and 190 Hz in drive-mode are also provided. The bandwidths of both modes are highly matched with each other, providing a bandwidth of 100 Hz for the entire system, thus illustrating that it could satisfy the requirements in practical applications. [ABSTRACT FROM AUTHOR]

The superior performance of a novel deflection-type multi-DOF actuator is introduced briefly in this paper, three kinds of permanent magnetic rotor magnetization modes and schemes for a new PM deflection-type multi-DOF motors have been put forward. Static magnetic flux density modulus value calculation and static magnetic field analysis of every kind of permanent magnet magnetization modes and key structure parameters are implemented, and then the detailed distribution features of the rotor in permanent magnet deflection-type multi-DOF motor are simulated under the circumstance of 3D finite element software. Finally some disciplines of NdFeB rotor are concluded and analyzed. The results provide the references for the structure design of such kind of actuators or motors. [ABSTRACT FROM AUTHOR]

The methods of multi-DOF actuator orientation detection based on machine vision and magnetic field sensor and neural network based multisensor fusion are presented in this paper. Special grid pattern is printed on the surface of rotor according to the pseudo-random encoder for the camera capturing the image of the rotor. The magnetic field sensors are adopted and properly placed circling the shaft of rotor for detection the orientation information. By analyzing the image of the rotor, the coordinates of characteristic points in the coordinate system fixed on the rotor are derived. Combined with the magnetic sensor scheme to reduce the measurement error and enhance the fault tolerant ability, a multisensor data fusion scheme using BP neural network is developed and validated by experiment. The results show that multisensor data fusion based on NN is superior to single measurement method with more accuracy and high reliability, which is more effective and practical for applications [ABSTRACT FROM AUTHOR]

In this paper governing equations of general multi degrees of freedom (dof) systems with trees of parallel Nonlinear Energy Sink (NES) devices at each dof are derived. Then these equations are summarized for a 4 dof structure with two parallel NES at the 4 dof in order to control the first mode of the system. A prototype four storey structure with two parallel NES at the top floor is studied experimentally. The NES of the mentioned system is designed by endowing the suggested method in the Part I of this paper. A couple of experimental tests are carried out on the structure at the DGCB laboratory of the ENTPE, France. The aim is to control the first mode of the compound nonlinear system by demonstrating the efficiency of the parallel NES systems on the intended task. [ABSTRACT FROM AUTHOR]

The superior performance of PM spherical Multi-DOF motors is introduced briefly in this paper, four kinds of permanent magnetic rotor design schemes for a new PM spherical Multi-DOF motors have been put forward. Static magnetic flux density modulus value calculation and static magnetic field analysis of every kind of permanent magnet structure are implemented, and then the torque features of permanent magnetic rotor structures in permanent magnet spherical multi-DOF motor are simulated under the circumstance of 3D finite element software. Finally the five cylinder structure of NdFeB rotor is manufactured instead of spherical structures. The experiment results demonstrate the effectiveness of the designed structure. [ABSTRACT FROM AUTHOR]

Abstract: Pneumatic actuators have several advantages such as light weight, safety, low cost and high compliance. However, many pneumatic actuators have complicated systems that include a compressor, air tubes, and pneumatic valves with electrical wires. This research proposes a new control method for a multiplex pneumatic transmission constructed with special resonant valves and air tubes with a control system driven by air vibration in air tubes without electrical wires. The control is simplified and effective for pneumatic systems having many degrees of freedom. In this paper, the development of a primitive model of the resonant valve and a prototype valve is described. In addition, two control methods, which are a superimposing method and a time-sharing method, are shown, and the independent driving of four actuators is realized by using one of the control methods with air tubes only. [Copyright &y& Elsevier]

A stochastic response spectrum method is proposed for simple evaluation of the structural response of an actively controlled aseismic structure. The response spectrum is constructed assuming a linear structure with an active mass damper (AMD) system, and an earthquake wave model given by the product of a non-stationary envelope function and a stationary Gaussian random process with Kanai-Tajimi power spectral density. The control design is executed using a linear quadratic Gaussian control strategy for an enlarged state space system, and the response amplification factor is given by the combination of the obtained statistical response values and extreme value theory. The response spectrum thus produced can be used for simple dynamical analyses. The response factors obtained by this method for a multi-degree-of-freedom structure are shown to be comparable with those determined by numerical simulations, demonstrating the validity and utility of the proposed technique as a simple design tool. This method is expected to be useful for engineers in the initial design stage for structures with active aseismic control. [ABSTRACT FROM AUTHOR]

A surface encoder incorporating an angle grid and two two-dimensional (2D) slope sensors is presented. The angle grid is a plate inscribed with periodic sinusoidal waves in the X and Y directions as a position reference, and the position of the plate is detected uniquely using two slope-sensor units. One of the slope sensors is fitted with a beam scanning function to probe and read the angle grid. The system provides two measurement modes: a high-speed measurement mode that measures the XYθz position at a fast sampling rate, and a multiple degree-of-freedom (DOF) measurement mode that measures the XYθxθyθz position at a lower sampling rate by probe scanning. The linearity, cross-talk and resolution of a prototype encoder system are evaluated, and the system is shown to be acceptable for application as a precise dual-mode measurement scheme for a planar stage. [Copyright &y& Elsevier]