Human–robot cooperation control based on a dynamic model of an upper limb exoskeleton for human power amplification

In this paper, we propose a human–robot cooperation controller for the motion of the upper limb exoskeleton. The system permits three degrees of freedom using an electrical actuator that is mainly controlled by force sensor signals. These signals are used to generate the torque required to drive the exoskeleton. However, singularities exist when the force signals in the Cartesian coordinate system are transformed into torques in the joint coordinate system. Therefore, we apply the damped least squares method. When handling a load, torque compensation is required about its mass. Therefore, we installed a force sensor at the point of the robot’s end-effector. It measures the forces between the exoskeleton and the load. Then, these forces are used to compensate within a static model for handling loads. We performed control stability and load handling experiments to verify the effectiveness of the controller. Via these, we confirmed the effectiveness of the proposed controller.     

Constrained haptic-guided shared control for collaborative human–robot percutaneous nephrolithotomy training

Percutaneous nephrolithotomy is a procedure used to treat patients with large or irregularly shaped kidney stones. Surgical instruments are inserted through a small incision to access the kidney and remove the calculi. Surgeons who have less experience with the procedure manifest significantly higher rates of complications due to the procedure’s steep learning curve. This issue is further exacerbated by a lack of training opportunities in clinical settings. This paper introduces a teleoperative framework that can provide training to surgeons as well as assistance during procedures, based on two main components. Firstly, a type of constrained inverse kinematics that decouples the tooltip position from its orientation using a remote centre of motion, and incorporates the joint limits analytically. This reduces the workload of the procedure by having the surgeon control only the tooltip position rather than the position and the orientation while preventing the inverse kinematics from returning joint angles outside of the robot’s abilities. This kinematic framework also allows a three-degrees-of-freedom haptic device to control a six-degrees-of-freedom manipulator. Secondly, haptic feedback is provided to help guide and teach the surgeon during the procedure. Haptic feedback allows the surgeon to remain in full control during the procedure while still receiving haptic cues and assistance.Experimental results indicate that the haptic cues improved user’s accuracy, and they had shorter and smoother paths. This leads to a shorter procedure time overall. The results also indicate that the haptic assistance helped teach users the ideal trajectory of the procedure and that users who were taught with haptic feedback performed better than those who never experienced any haptic feedback.     

Identification of human control law during physical Human–Robot Interaction

With the growing interest in applications involving humans and robots teaming together, the need to understand each other’s intentions and behavior arises. This work presents a method to online identify the time-varying human feedback control law during physical Human–Robot Interaction. The robot motion is implemented as a Cartesian impedance, and the interaction with the human happens by force exchange. The coupled system is modeled with a state-space formulation. The state vector is augmented with the unknown parameters, and an Extended Kalman Filter (EKF) is implemented for online identification. This approach is compared with the Least Squares (LS) and the Recursive Least Squares (RLS) methods. Both simulation and experimental results are provided, showing the presented approach’s feasibility in identifying the parameters and reconstructing the control inputs.     

Distributed nonlinear model predictive control of an autonomous tractor–trailer system

This paper addresses the trajectory tracking problem of an autonomous tractor–trailer system by using a fast distributed nonlinear model predictive control algorithm in combination with nonlinear moving horizon estimation for the state and parameter estimation in which constraints on the inputs and the states can be incorporated. The proposed control algorithm is capable of driving the tractor–trailer system to any desired trajectory ensuring high control accuracy and robustness against environmental disturbances.     

H∞ control of a flexible gantry robot arm using smart actuators

This paper presents new feedback actuators to achieve an accurate position control of a flexible gantry robot arm. The translational motion in the plane is generated by two d.c. motors and controlled by electro-rheological (ER) clutch actuators. The generated motion can be continuously controlled by controlling the intensity of electric fields imposed to the ER fluid domains of bi-directional rotating ER clutches. On the other hand, during control action of the translational motion, a flexible arm attached to the moving part produces undesirable oscillations due to its inherent flexibility. The oscillations are actively suppressed by employing feedback voltage to the piezoceramic actuator bonded on the surface of the flexible arm. Consequently, an accurate position control at the end-point of the flexible arm can be achieved. In order to accomplish this control target, the governing equations of the proposed system are derived and rewritten as transfer functions to design a robust H_∞ controller. The control electric fields to be applied to the ER clutch and the control voltage for the piezoceramic actuator are determined via the loop shaping design procedures (LSDP) in the H_∞ control technique. Control results of position regulating and tracking are provided to evaluate the effectiveness of the proposed methodology.     

Digital modular control of high frequency DC–DC converters

This paper presents a solution for controlling integrated DC–DC converters with high switching frequency (>20 MHz). The increase of the switching frequency is a trend biased by output filter volume restrictions and integration demand. The control of DC–DC converters operating at high frequency presents an opportunity to speed up the converter response time but also a challenge specially for the control solution, quiescent current and to limit the sensitivity to process and operating conditions for the mixed signal circuits involved. The solution presented in this work relies on separating the duty-cycle into three parts: a load-free value that depends only on the input and output voltages, a transient fast correction contribution, and an accurate compensation for the IR drop that depends on the load current. The load-free portion of the duty-cycle has a compensation of PVT variations and the fast transient part of the duty-cycle uses a non-linear sliding mode control solution. All the analog blocks required for the implementation of the proposed solution are detailed.     

Position control of a pneumatic surgical robot using PSO based 2-DOF H∞ loop shaping structured controller

This research proposed novel development of a 2-DOF H_∞ loop shaping structured controller based on Particle Swarm Optimization (PSO) that considers the closed-loop dynamic response, robustness, stability, and minimal control input in design criteria to control position of 3-DOF pneumatic surgical robot. Unlike other conventional H_∞ controllers, the proposed controller offers robustness, high performance, but cost-effective simple structure, which has recently received attention from several researchers and preferred in industrial applications. The proposed technique is simulated and experimented on a nonlinear system of a pneumatic 3-DOF surgical robot for a Minimally Invasive Surgery (MIS). Mechanical design, dynamics modeling, and system identification of the surgical robot are conducted. The simulation results verify that the proposed controller can gain a better H_∞ sub-optimal solution than the conventional 2-DOF H_∞ loop shaping controller. Also, the experiments confirm that the proposed controller is capable to tolerate the perturbed conditions and can be alternative to the conventional controllers in pneumatic controlled system     

A model for concept evaluation in design––an application to mechatronics design of robot grippers

In this paper, an approach for the modelling of the evaluation process in the conceptual design phase is presented. During the design process, the generated candidate solutions are evaluated. The evaluation is achieved by calculating a score that is based on specific criteria that are presented as elements of a vector. Weight factors are applied to highlight the importance of each criterion. The formulation of the evaluation score is based on t-norm and averaging operators with the assumption that the universe of discourse of criteria is [0,1]. A discussion of the meaning of these operators and a comparative study of them is presented. As an application, the mechatronics design of robot grippers for handling fabrics is analysed. The elements of the mechatronics index are presented in terms of flexibility, intelligence and complexity. This index is formulated using the variety of the t-norms and averaging operators to show the weaks and strengths of each of them.     

Switching-type fuzzy sliding mode control of a cart–pole system

The theme for a switching-type fuzzy sliding mode controller for the cart–pole system is developed in this paper. The control strategy is to make a vertical pole straight up and regulate the position of cart simultaneously. This system is nonlinear, unstable and nonminimum phase in consideration of these two control purposes; the conventional control algorithms are difficult to solve such a problem because only one control input can be utilized. By taking the experience of balancing a pole by a finger, we divide the dynamic response of the cart–pole system into approaching and departure conditions. Then the cart can be directed to the desired location with a balanced pole by switching two types of fuzzy sliding mode controllers. The feasibility and robustness of the proposed algorithm are demonstrated by computer simulations and actual experimental results.     

Fuzzy control of dc–dc converters based on user friendly design

The aim of this paper is to show how to build a fuzzy controller and its membership functions automatically. In a fuzzy logic controller (FLC), the proposed method allows one easily to construct a set of membership functions, called shrinking-span membership functions (SSMFs). The FLC uses Mamdani-type fuzzy controllers for the defuzzification strategy and inference operators. The FLC hardware implementation is performed on an 8-bit microcontroller. Simulation results and experimental results demonstrate that the converter can be regulated with good performance even when subjected to input disturbance and load variation. The presented approach is generally valid for the design of an FLC, and can be applied to any dc–dc converter topologies.     

Amplitude regeneration of NRZ–DPSK signal with a feed-forward control circuit

An optical-and-electrical hybrid-type amplitude regenerator for an NRZ–DPSK signal suffering from optical amplifier noise is described. The system is a feed-forward control circuit composed of a coupler, a photo detector, and an intensity modulator, and works to suppress intensity fluctuations in a DPSK signal while preserving phase information. A schematic explanation of how the DPSK transmission performance is improved with intensity noise suppression during transmission is presented, and an experiment to demonstrate its effect is conducted.     

Development of parallel-connected pump–valve-coordinated control unit with improved performance and efficiency

Recently, there has been a growing demand for electro-hydraulic systems that can offer both high control performance and high energy efficiency. Traditionally, high performance is achieved using expensive high-bandwidth servo valve-controlled units. However, the inevitable throttling losses that occur in such systems severely decrease their energy efficiency. For a higher energy efficiency, pump-controlled systems have become the standard choice in this field. Nevertheless, their dynamic performance is inferior to that of valve-controlled systems. Considering the individual advantages of the valve- and pump-controlled units, our previous work proposed the idea of a parallel-connected pump–valve-coordinated system. In this study, a generic form of the coordinated control unit is discussed, and further improvements are made to the control design. In addition, comprehensive experimental studies are conducted with a variable-displacement pump and a servo motor-driven pump equipped with a direct pump-control component. Favorable results are obtained, demonstrating that the proposed system can achieve better tracking performance than a typical valve-controlled system, while simultaneously improving the energy efficiency.     

Finite-time control of DC–DC buck converters via integral terminal sliding modes

This article presents novel terminal sliding modes for finite-time output tracking control of DC–DC buck converters. Instead of using traditional singular terminal sliding mode, two integral terminal sliding modes are introduced for robust output voltage tracking of uncertain buck converters. Different from traditional sliding mode control (SMC), the proposed controller assures finite convergence time for the tracking error and integral tracking error. Furthermore, the singular problem in traditional terminal SMC is removed from this article. When considering worse modelling, adaptive integral terminal SMC is derived to guarantee finite-time convergence under more relaxed stability conditions. In addition, several experiments show better start-up performance and robustness.     

Itakura–Saito Divergence as an Element of the Information Theory of Speech Perception

Journal of Communications Technology and Electronics - On the basis of the information theory of speech perception, a substantiation of the symmetric form of the Itakura–Saito divergence as...     

Model predictive control of bidirectional isolated DC–DC converter for energy conversion system

Model predictive control (MPC) is a powerful and emerging control algorithm in the field of power converters and energy conversion systems. This paper proposes a model predictive algorithm to control the power flow between the high-voltage and low-voltage DC buses of a bidirectional isolated full-bridge DC–DC converter. The predictive control algorithm utilises the discrete nature of the power converters and predicts the future nature of the system, which are compared with the references to calculate the cost function. The switching state that minimises the cost function is selected for firing the converter in the next sampling time period. The proposed MPC bidirectional DC–DC converter is simulated with MATLAB/Simulink and further verified with a 2.5 kW experimental configuration. Both the simulation and experimental results confirm that the proposed MPC algorithm of the DC–DC converter reduces reactive power by avoiding the phase shift between primary and secondary sides of the high-frequency transformer and allow power transfer with unity power factor. Finally, an efficiency comparison is performed between the MPC and dual-phase-shift-based pulse-width modulation controlled DC–DC converter which ensures the effectiveness of the MPC controller.     

A multiple-output switched-capacitor DC–DC converter for individual brightness control of RGB LEDs with time-interleaved control and output current regulation

In this paper, an integrated multiple-output switched-capacitor (SC) converter with time-interleaved control and output current regulation is presented. The SC converter can reduce the number of passive components and die areas by using only one flying capacitor and by sharing active devices. The proposed converter has three outputs for individual brightness control of red–green–blue (RGB) LEDs. Each output directly regulates the current due to the V–I characteristics of LEDs, which are sensitive to PVT variations. In the proposed converter, the current-sensing technique is used to control the output current, instead of current-regulation elements (resistors or linear regulators). Additionally, in order to reduce the active area, three outputs share one current-sensing circuit. In order to improve the sensing accuracy, bias current compensation is applied to a current-sensing circuit. The proposed converter has been fabricated with a CMOS 0.13-μm 1P6M CMOS process. The input voltage range of the converter is 2.5–3.3 V, and the switching frequency is 200 kHz. The peak power efficiency reaches 71.8 % at V _IN =2.5 V, I _LED1 = 10 mA, I _LED2 = 18 mA, and I _LED3 = 20 mA. The current variations of individual outputs at different supply voltages are less than 0.89, 0.72, and 0.63 %, respectively.     

Cascade position control of a single pneumatic artificial muscle–mass system with hysteresis compensation

The inherent hysteresis in a pneumatic artificial muscle (PAM) makes it difficult to control accurately the position of the PAM’s end effector. This hysteresis causes energy loss and the area of the hysteresis loop is dependent on the amplitude of the motion and on the underlying causes of the hysteresis phenomenon. This means that if the hysteresis energy loss is properly compensated, a more accurate positioning would be achieved. In this paper, the pressure/length hysteresis of a single PAM is modeled by using a Maxwell-slip model. The obtained model is used in the feedforward path of a cascade position control scheme, in which the inner loop is designed to cope with the nonlinearity of the pressure buildup inside the PAM, whereas the outer loop is designed to cope with the nonlinearity of the PAM dynamics itself. The experimental results show that position control of a single PAM–mass system with hysteresis compensation (HC) is effectively improved compared to a control without HC, and the control system shows high robustness to load changes.     

A method for the amplitude–phase synthesis of antenna array based on control of the set of nonidentical partial beams

An iterative method for the amplitude–phase synthesis of antenna arrays based on control of the set of partial beams is proposed. In this method, two additional partial beams are added to the radiation pattern at each step. The shape of each beam is optimized with consideration for the difference between the synthesized and specified radiation patterns. Parameters specifying the shape of additional partial beams are chosen with the help of the genetic algorithm. The results of numerical studies allowing comparison of the proposed synthesis method to the least-squares method and the method based on control of the set of identical partial beams are presented.     

Local lifetime control by light ion irradiation: impact on blocking capability of power P–i–N diode

The impact of local lifetime control by ¹H⁺ and ⁴He²⁺ irradiation on blocking characteristics of power P–i–N diodes was studied in the dose range up to 5×10¹² cm⁻². Energies and doses for both types of projectiles were chosen in a way to create a comparable damage in three qualitatively different regions close to the anode junction. Blocking capabilities of irradiated diodes were measured, compared and simulated. The results show that there is no difference between hydrogen and helium irradiation if the damage is located inside the anode area. When the damage peak is placed into the N-base side of the anode junction and the dose of protons exceeds 10¹²  cm⁻², blocking capability of the diode drastically decreases while it stays at the same level for analogous irradiation by helium ions.