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In the active vibration reduction of two-dimensional structures, piezoelectric actuators of regular shapes, e.g. rectangular, circular, are commonly used. However, the shape of the transducers can be irregular, asymmetric (a-PZT), and its geometry can be an object for optimization. The paper presents an experimental validation of the application of optimal shaped a- PZT in the active reduction of triangular plate vibrations. Optimization was based on the criterion of the maximum bending moment. This means that the center of a-PZT is located at the point where the bending moment of the plate has reached its absolute maximum. The isosceles right triangular plate with simply supported edges was chosen as the research object. The research confirms the validity of the criterion used for optimization and may be an introduction to considering the use of optimal a-PZT in the active reduction of vibrations for more complex structures.

For the VSC-HVDC system transmitting new energy， poor parameter matching between the new energy controller and the VSC-HVDC controller can lead to sub-synchronous and super-synchronous oscillation. To address this， an open-loop strategy based on virtual synchronous generator （VSG） control has been adopted. This strategy eliminates the inner and outer loops and the phase lock of traditional closed-loop control methods， optimizing the impedance characteristics of the VSC-HVDC system and reducing the risk of sub-synchronous and super-synchronous oscillations of new energy. It is also compatible with both islanded and grid-connected operating modes. To address bipolar power imbalance and excessive short-circuit current after faults in open-loop control， bipolar power balancing and fault ride-through （FRT） strategies have been proposed. The effectiveness of the proposed VSG control and FRT strategies has been validated through RTDS simulations.

Abstract The architecture and a flight test campaign of a small‐scale testbed aimed at aerodynamic and dynamic characterization of airborne wind energy systems are presented. The testbed involves a two‐line rigid‐framed delta kite and an automatic ground station for the lateral control of the kite and reel‐in/reel‐out of the two tethers. The environment, and the states of the kite, the tethers and the actuators are measured by a set of on‐ground and onboard sensors that include, among others, an inertial measurement unit, GNSS receivers, load cells, actuator encoders, a wind station, and a visual motion tracking (VMT) system based on three cameras and an artificial neural network (YOLOv2). The results of a 5‐min flight, including the take‐off, cross‐wind flight, and landing, were used to analyze the capabilities of the testbed. It was shown that the time derivative of the kite course angle exhibits a linear correlation with both the delayed steering input and the delayed differential tether tension, being the dispersion lower for the latter. The intrinsic and extrinsic calibrations proposed for the VMT system led to a good agreement between the estimation of the kite position and course angle provided by the VMT system and the onboard computer. Moreover, although the YOLOv2 algorithm failed in the detection of the kite within around 5% of the images, the simultaneous non‐detection from the three cameras was below 0.1% during the full flight. Such a reliability suggests that a VMT system can be used as a redundant or backup sensor for the GNSS.

Soft robots distinguish themselves from traditional robots by embracing flexible kinematics. Because of their recent emergence, there exist numerous uncharted territories, including novel actuators, manufacturing processes, and advanced control methods. This research is centred on the design, fabrication, and control of a pneumatic soft robot. The principal objective is to develop a modular soft robot featuring multiple segments, each one with three degrees of freedom. This yields a tubular structure with five independent degrees of freedom, enabling motion across three spatial dimensions. Physical construction leverages tin-cured silicone and a wax-casting method, refined through an iterative processes. PLA moulds that are 3D-printed and filled with silicone yield the desired model, while bladder-like structures are formed within using solidified paraffin wax-positive moulds. For control, an empirically fine-tuned open-loop system is adopted. This paper culminates in rigorous testing. Finally, the bending ability, weight-carrying capacity, and possible applications are discussed.

This paper designs an optimal open-loop leader-follower control strategy of input-delay stochastic systems. The leader-follower control problem is described as an optimal problem based on Stackelberg strategies. A control strategy of the leader is given to minimize the function of $H_{2}$ norm, while a control strategy of the follower in worst case maximizing the function of $H_\infty $ norm is applied to the systems. Then the optimal leader-follower control strategy is obtained by establishing the information relationship of the forward and the backward variables with augmentation of the variables and solving several Riccati equations. At last, an example illustrates the effectiveness of the proposed strategy.

This paper introduces a new gripper mechanism that is capable of grasping objects of various sizes and shapes without the need for a closed-loop control system. Industries such as the food and beverage industry are seeking innovative soft grippers with a simplified control system. The proposed design utilizes a rotary mechanism with springs to achieve both force-closure and form-closure grasping. The design sets itself apart from most soft grippers with its ability to offer grasping forces in all lateral directions. The gripper is designed in a cylindrical shape and is actuated by a stepper motor with a gearbox to enhance the torque. Three stacked curvilinear and linear rails convert the motor’s rotational motion into linear motion. The grasping component consists of three curved parts, each incorporating numerous compression springs. Currently, the gripper can effectively grasp objects ranging from five to nine centimeters in diameter, with a maximum height of ten centimeters. However, the design is scalable based on specific application requirements. A comprehensive CAD model of the mechanism was developed, and multiple analyses were conducted, including motion, topology, and stress analyses. Finally, a functional prototype of the gripper was constructed and successfully tested for grasping fruits and vegetables of different sizes and shapes. This research can be further expanded to explore the application of the gripper in space exploration with its novel and completely electro-mechanical foundation.

The paper proposes an algorithm for solving the optimal open-loop terminal control problem of two spacecraft rendezvous with constraints on their states. A system of nonlinear differential equations that describes the dynamics of the active (maneuvering) spacecraft relative to the passive spacecraft (station) in the central gravitational field of the Earth in the orbital coordinate system of coordinates related to the passive spacecraft center-of-mass is considered as an initial model. The obtained nonlinear model of the active spacecraft dynamics is linearized relative to the specified reference state trajectory of the passive spacecraft, and then it is discretized and reduced to linear recurrence relations. Mathematical formalization of the spacecraft rendezvous problem under consideration is carried out at a specified final moment of time for the obtained discrete-time controlled dynamical system. The quality of solving the problem is estimated by a convex functional taking into account the geometric constraints on the active spacecraft states and the associated control actions in the form of convex polyhedral-compacts in the appropriate finite dimensional vector space. We propose a solution of the problem of optimal terminal control over the approach of the active spacecraft relative to the passive spacecraft in the form of a constructive algorithm on the basis of the general recursive algebraic method for constructing the availability domains of linear discrete controlled dynamic systems, taking into account specified conditions and constraints, as well as using the methods of direct and inverse constructions. In the final part of the paper, the computer modeling results are presented and conclusions about the effectiveness of the proposed algorithm are made.

The paper deals with an optimal control problem in a dynamical system described by a linear differential equation with the Caputo fractional derivative. The goal of control is to minimize a Bolza-type cost functional, which consists of two terms: the first one evaluates the state of the system at a fixed terminal time, and the second one is an integral evaluation of the control on the whole time interval. In order to solve this problem, we propose to reduce it to some auxiliary optimal control problem in a dynamical system described by a first-order ordinary differential equation. The reduction is based on the representation formula for solutions to linear fractional differential equations and is performed by some linear transformation, which is called the informational image of a position of the original system and can be treated as a special prediction of a motion of this system at the terminal time. A connection between the original and auxiliary problems is established for both open-loop and feedback (closed-loop) controls. The results obtained in the paper are illustrated by examples.

This paper presents an experimental approach for the design of a brushless DC (BLDC) motor-driven pump that is intended to pump fluids with unknown specific gravity. We propose a control mechanism that will enable the pump to operate at a higher efficiency irrespective of fluid types. Experimental results from a prototype pump system controlled by two different open-loop controllers are used for determining the optimized closed-loop control algorithm to run the pump while tracking its higher efficiency point. A set of computer simulations is conducted based on a conventional finite-element method to design the best possible BLDC motor, which is employed in the proposed fault-tolerant and efficient pump. Experimental results are presented to validate the efficiency of the proposed pump and also compared with that of a commercial motor design simulator.

To improve the linearisation of the variable flow-regulate system under the open-loop control, a proportional solenoid valve with high-linearity performance was developed to meet that requirement of the high-precision and open-loop control. The design of the proportional solenoid valve evolves the optimisation of a magnetic circuit structure, the construction of a balanced pressure structure and the compensation of a feedforward control device. As for the solenoid, it is very challenging to meet the requirement of 95% linearity. A feedforward control device with the Bouc–Wen model and a quadratic inverse function model is a good solution to address the hysteresis problem and achieve better performance. The optimisation of a simple magnetic circuit with low sensitivity to the moving armature and a balance chamber for removing the pressure difference are both preconditions to make the compensation. The feedforward control device is the next step to eliminate the hysteresis problem and non-linear characteristics of the solenoid by solving model coefficients measured in the test. After the improvement in these aspects, the proportional solenoid valve can meet the demand of digital proportional flow control with >98% linearity and excellent repeatability, through the validation of both no-load and high-load performance tests.

This study proposed an approach to control voice coil motors (VCMs) installed in smartphone modules as autofocus actuators. The VCM developed in this study comprises guide rods. The magnetic field attraction force between guide rods and movable parts serves as lens restoring force. This study did not use feedback elements to avoid the stick-slip phenomenon between VCM guide rods and movable parts. Instead, this study used a high-low frequency composite signal based on the findings from a mathematical model analysis and VCM dynamic attribute analysis, preventing stick-slip and offering the VCM a more favorable positioning precision.

Stable maneuverability is extremely important for the overall safety and robustness of autonomous vehicles under extreme conditions, and automated drift is able to ensure the widest possible range of maneuverability. However, due to the strong nonlinearity and fast vehicle dynamics occurring during the drift process, drift control is challenging. In view of the drift parking scenario, this paper proposes a segmented drift parking method to improve the handling ability of vehicles under extreme conditions. The whole process is divided into two parts: the location approach part and the drift part. The model predictive control (MPC) method was used in the approach to achieve consistency between the actual state and the expected state. For drift, the open-loop control law was designed on the basis of drift trajectories obtained by professional drivers. The drift monitoring strategy aims to monitor the whole drift process and improve the success rate of the drift. A simulation and an actual vehicle test platform were built, and the test results show that the proposed algorithm can be used to achieve accurate vehicle drift to the parking position.

Stepper motors are widely used in many applications where discrete, precise movement is required. There is a variety of dedicated stepper motor controllers (sometimes referred to as “step sticks”) available on the market. Those controllers provide a number of different motor control schemes that vary by aspects like current control method, reference current shape or maximum resolution increase (microstepping). The two most widely acknowledged signal shapes are sine-cosine microstepping and quadrature microstepping. The choice of the control scheme impacts torque output, torque variation, positioning error and maximum power supply requirements. This paper presents a family of generalised microstepping signal shapes, ranging from sine-cosine microstepping to quadrature microstepping. Derivation of signal shapes as well as their mathematical analyses are provided. Those signals are then implemented on the control board. A series of experiments is performed on a test bench to analyse the influence of different signal shapes on the performance of the motor in both load and no load conditions. The comparison of the new generalized shapes influence on the motor operation to the commonly used sine-cosine and quadrature control is provided.

In this paper we consider a four-dimensional bioreactor model, describing an anaerobic wastewater treatment with methane production. Different control strategies for stabilizing the dynamics are presented and discussed. A general and practice-oriented bounded open-loop control is proposed, aimed to steer the model solutions towards an a priori given set in the phase plane.

OPTCON is an algorithm for the optimal control of nonlinear stochastic systems which is particularly applicable to economic models. It delivers approximate numerical solutions to optimum control (dynamic optimization) problems with a quadratic objective function for nonlinear economic models with additive and multiplicative (parameter) uncertainties. The algorithm was first programmed in C# and then in MATLAB. It allows for deterministic and stochastic control, the latter with open loop (OPTCON1), passive learning (open-loop feedback, OPTCON2), and active learning (closed-loop, dual, or adaptive control, OPTCON3) information patterns. The mathematical aspects of the algorithm with open-loop feedback and closed-loop information patterns are presented in more detail in this paper.

This paper deals with the development of an open-loop controller implemented in the Arduino platform in order to reuse an existing CNC machine for performing simple manufacturing operations. The CNC machine considered in this study is an Objet Quadra Tempo 3D printer. The goal of this work is, therefore, to convert the machine, considered obsolete due to high maintenance costs, by using low-cost off-the-shelf components and by using open source software in order to reduce the amount of electronic and industrial wastes by means of simple retrofitting operations. To control the drivers of the stepper motors of the machine, an ArduinoMega 2560 microcontroller was used. The Arduino micro-controller allows for controlling analog and digital devices in a straightforward manner. All retrofitting operations were conducted in order to carry out additive manufacturing and subtractive manufacturing operations. For the activity reported in this paper, an electro-spindle for machining products in wood and polycarbonate was installed. The use of low-cost components allowed the transformation of the 3D printer into a CNC milling machine capable of working materials such as wood and polycarbonate.

Temperature control is the most important and fundamental part of a polymerase chain reaction (PCR). To date, there have been several methods to realize the periodic heating and cooling of the thermal-cycler system for continuous-flow PCR reactions, and three of them were widely used: the thermo-cycled thermoelectric cooler (TEC), the heating block, and the thermostatic heater. In the present study, a new approach called open-loop controlled single thermostatic TEC was introduced to control the thermal cycle during the amplification process. Differing from the former three methods, the size of this microdevice is much smaller, especially when compared to the microdevice used in the heating block method. Furthermore, the rising and cooling speed of this method is much rapider than that in a traditional TEC cycler, and is nearly 20–30% faster than a single thermostatic heater. Thus, a portable PCR system was made without any external heat source, and only a Teflon tube-wrapped TEC chip was used to achieve the continuous-flow PCR reactions. This provides an efficient way to reduce the size of the system and simplify it. In addition, through further experiments, the microdevice is not only found to be capable of amplification of a PCR product from Human papillomavirus type 49 (Genbank ref: X74480.1) and Rubella virus (RUBV), but also enables clinical diagnostics, such as a test for hepatitis B virus.

This paper describes an input shaping method based on an experimental transfer function to effectively obtain a desired scan output for an electrostatic microscanner driven in a quasistatic mode. This method features possible driving extended to a higher frequency, whereas the conventional control needs dynamic modeling and is still ineffective in mitigating harmonics, sub-resonances, and/or higher modes. The performance of the input shaping was experimentally evaluated in terms of the usable scan range (USR), and its application limits were examined with respect to the optical scan angle and frequency. The experimental results showed that the usable scan range is as wide as 96% for a total optical scan angle (total OSA) of up to 9° when the criterion for scan line error is 1.5%. The usable scan ranges were degraded for larger total optical scan angles because of the nonlinear electrostatic torque with respect to the driving voltage. The usable scan range was 90% or higher for most frequencies up to 160 Hz and was drastically decreased for the higher driving frequency because fewer harmonics are included in the input shaping process. Conclusively, the proposed method was experimentally confirmed to show good performance in view of its simplicity and its operable range, quantitatively compared with that of the conventional control.

This paper presents the design and implementation of a DSP-based controller for a super high-speed (>80,000 rpm) permanent magnet synchronous motor (PMSM). The PMSM is a key component of the centrifugal compressor drive of a reverse Brayton cryocooler that is currently under development for NASA and Florida Solar Energy Center. The design of the PMSM open-loop control is presented. Experimental results with open-loop control schemes are presented. System optimization and analysis are also illustrated. They verify the effectiveness of the controller design and the optimization scheme.

In this paper we examine the application of evolutionary algorithms to find open-loop control solutions of the optimal control problem arising from the semidiscretisation of a linear parabolic tracking problem with boundary control. The solution is compared with the solutions obtained by methods based upon the variational equations of the Minimum Principle and the finite element method.