A Capacitive Impedance Control Method for Active Capacitor with Adaptive Parameter Capability

A walking assistance apparatus which can promote gait training for motor palsy patients and outdoor walking for the elderly was developed. Our prototype uses a novel spatial parallel link mechanism and restraint free type of equipment. The apparatus supports complete leg alignment, including the soles of the feet from under the soles with flat steps, and assists walking behavior at the ankle, knee, and hip joints simultaneously without the use of Velcro tape. We proposed the control method according to the purpose of the user. For example, to promote gait training, this apparatus can select the impedance control method. User's legs are assisted along the trajectory with the ideal gait as well as walking. To promote outdoor walking for the elderly, this apparatus can select the torque control method. The apparatus calculates the necessary torques of each joint according to the posture and motion of the apparatus and user. In the case of the impedance control method, by adjusting the natural frequency of the ideal dynamic equation for the flat steps under the soles, the user felt it was easier to walk by frequency entrainment. On the other hand, to promote outdoor walking of the user, this apparatus has to be used not only on the flat ground but also on stairs or slopes with freedom behaviors, and it has to make the user feel comfortable. To address this problem, the torque control method proposed to use real-time acceleration data instead of using the template trajectory. By using this method, the subject could walk on the slope and stairs continuously. Finally, %MVC of the user's EMG while walking equipped with this apparatus was measured, and the influence of the difference using between the impedance and torque control method was confirmed by interviewing the subjects. From the result, the impedance control method assisted the motion of kicking the ground, and the torque control method assisted the motion of raising-up the leg. Therefore, the impedance control method is good for gait training, and the torque control method is good for walk promotion.

In this paper, a novel impedance control method is designed for the hydraulic drive unit (HDU) equipped on the hydraulic driven legged robot. First, the position control mathematical model of HDU is built. Next, the HDU performance test platform is introduced and the performance requirements are given. Second, the system load pressure observer is designed and an accurate stiffness control method is proposed by combining the external load force feed forward control with the load force feedback control. Third, the damping control method based on the velocity feedback is designed. Finally, a novel impedance control method is proposed through combining the stiffness control and the damping control. The effects of all techniques listed above have been verified experimentally. Especially, the impedance control effects are verified by comparing the impedance characteristics with the natural characteristics of the second-order mass-spring-damper system. This research indicates that the system characteristics of HDU with the novel impedance control method is well equivalent to that of the second-order mass-spring-damper system, which can solve the stall problem of the robot joint movement process caused by the load force vanish instantaneously and the switch between position control and force control. The above research can provide references for the active compliance control of bionic legged robots.

This paper proposes an intelligent massage control system by using multi-fingered robot hand with hybrid impedance and force control, which is able to create the movement and force of robot to behave as similar as the human’s massage. Therefore, the various massage points, such as the changing of hardness and softness of human skin muscle condition, can be appropriately controlled by using hybrid impedance and force control method. The impedance control is used to control the lateral position of massage on the human skin muscle. The perpendicular direction one, while force control is carried out for the vertical direction on human skin muscle. This paper also gives a modeling of human skin muscle through robot perception of impedance to decide the parameter of impedance controller. The control strategy using a hybrid impedance and force control to implement an adaptive control system is presented, when human condition is changed with soft and hard skin muscle. For the robot fingertip force, PI servo compensation is used together with impedance control. Based on using both impedance and PI servo compensation, the effectiveness of the massage position and force control is shown through actual massage motion experiments.

This paper proposes an intelligent massage control system by using multi-fingered robot hand with hybrid impedance control, which is able to create the movement and the force of robot such as the human's massage. Therefore, the various massage points, such as the change of the stiffness of human skin muscle, can be controlled by using impedance control method. The hybrid impedance control is comprised of the two methods of the position-based and the force-based impedance control were applied. The position-based impedance control is used to control the lateral position of massage on the human skin muscle. On the other hand, the force-based impedance control is used to control the force of the vertical direction on human skin muscle. This paper also gives the identification of human skin muscle through robot perception of impedance to decide the parameter of impedance controller. The control strategy using impedance control to implement an adaptive control system is presented, when human condition is changed with soft and hard skin muscle. Effectiveness of massage control system by using multi- fingered robot hand with hybrid impedance control is demonstrator through actual massage experiments of pushing and rubbing motion.

Currently, a bottleneck problem for battery-powered microflying robots is time of endurance. Inspired by flying animal behavior in nature, an innovative mechanism with active flying and perching in the three-dimensional space was proposed to greatly increase mission life and more importantly execute tasks perching on an object in the stationary way. In prior work, we have developed some prototypes of flying and perching robots. However, when the robots switch between flying and perching, it is a challenging issue to deal with the contact between the robot and environment under the traditional position control without considering the stationary obstacle and external force. Therefore, we propose a unified impedance control approach for bioinspired flying and perching robots to smoothly contact with the environment. The dynamic model of the bioinspired robot is deduced, and the proposed impedance control method is employed to control the contact force and displacement with the environment. Simulations including the top perching and side perching and the preliminary experiments were conducted to validate the proposed method. Both simulation and experimental results validate the feasibility of the proposed control methods for controlling a bioinspired flying and perching robot.

In this work, an impedance control method is developed and applied to two cable-driven mechanisms. The first one is a classical problem of driving a rigid body in 3-D space by seven cables. Our approach is based on the impedance control of rigid link manipulators which is then extended to include the specific considerations of the cable-driven mechanisms such as maintaining the tensile force in the cables. The method is then extended to the serial multibody cable-driven mechanisms. The motivation for this problem is the possible application of cable-driven systems in the rehabilitative exercises such as physical and/or occupational therapies. In this case, the human body acts as a multibody system which is driven by cables attached. The impedance control in such application facilitates the comfort of the patient by providing the necessary compliance while moving the body parts. The formulation of the problem is developed using Lagrange’s equation and the control input (which is the cable forces) is calculated based on the position and/or force feedback from the multibody. Simulation results demonstrate the effectiveness of the presented method.

This paper presents a vibration control methodology that is useful in practical applications where the system to be controlled is difficult to model due to the presence of uncertainties or complex boundary conditions. The impedance control method uses a power flow approach wherein the controller is designed such that power flow into the structure is minimized. This is accomplished by using the dereverberated point impedance function at the actuator location for the design of the controller. The method is implemented and simulated for a cantilever beam with piezoceramic actuators. As a preliminary step towards real-time implementation of impedance control a simple state feedback algorithm is implemented using a dSPACE digital signal processor (DSP) card.

일반 산업용 로봇의 위치정밀도는 100㎛ 정도임에 반해, 정밀부품의 조립공차는 수십 ㎛ 이내이다. 또한, 조립공차가 작을 경우 미소한 위치/각도 오차에 의해 재밍 또는 웨징이 쉽게 발생하며, 위치제어 기반의 로봇인 경우 부품 조립 시 접촉력을 적절히 조절하지 못하여 조립물이 파손될 가능성이 크다. 이와 같은 문제를 해결하기 위하여 접촉력에 능동적으로 반응할 수 있는 힘제어 기반의 로봇조립에 대한 연구가 진행되고 있다. 본 연구에서는 기존의 산업용 로봇에 적용하기 용이하도록 위치제어 기반의 머니퓰레이터에 힘제어를 적용할 수 있는 시스템을 구현하였다. 머니퓰레이터에 어드미턴스 필터를 이용한 임피던스 제어를 적용하여 안정적인 접촉운동을 구현하였다. 또한, 임피던스 제어와 blind 검색을 적용하여 정밀부품을 조립할 수 있음을 검증하였다.

Impedance control is one of the most effective control methods for interaction between a manipulator and task environments. The force resulted by the interaction, however, does not occur until the end-effector of the manipulator touches its environment. A non-contact impedance control method has been proposed in order to achieve the impedance control before the contact. The method can regulate not only the end-point impedance but also the virtual impedance such that the end-effector is surrounded by a virtual object which can touch the environment before a real contact. This paper proposes a learning method using neural networks to regulate the virtual impedance parameters for given tasks. The validity of the method is verified through computer simulations and experiments with a conventional robot manipulator.

The traditional low-frequency oscillation suppression strategy in power systems relies on the POD (power oscillation damping) method to derive oscillation deviation signals, but this method is susceptible to interference from lead lag compensation, resulting in limited effectiveness in suppressing low-frequency oscillations. In view of this, the article developed a new method for low-frequency oscillation suppression based on self impedance control. Specifically, a low-frequency oscillation suppression model for the power system was first constructed, and the relevant suppression parameters were adjusted through self impedance control technology. Subsequently, a specialized low-frequency oscillation suppressor was designed to achieve effective control of low-frequency oscillations in the power system. Experimental verification shows that the self impedance control method not only has significant suppression effect, but also performs well in terms of deviation peak, oscillation frequency, recovery time, etc., exhibiting good nonlinear characteristics and fast attenuation speed. In addition, this method also has high reliability and practical value, providing strong support for reducing safety risks in power system operation.

Many systems and control methods have been proposed as mobility supports for the physically disabled and elderly individuals. In this research, we focus on a wearable-type system that supports the elderly with their walking. Different from typical control methods of wearable-type walking support systems, we propose a simple control method based on the spring–mass model. As a walking aid that does not require additional motions, such as sit-to-stand, this simple system is beneficial for two reasons. First, it reduces the calculation cost of deriving the support joint torque of the user; second, the wearable device hardware can be simply constructed from low-power actuators and springs rather than high-power actuators. In stance phase support mode, our motion control method compensates for a part of the force applied to the upper body as a leg muscle support. During the swing phase, walking is supported by a trajectory-following method using the impedance control as well as the spring–mass model. The proposed methods are applied to a prototype of a wearable-type walking support system, and evaluated in a series of experiments on human subjects.

This article attempts to review papers on power assist rehabilitation robots, human motion intention, control laws, and estimation of power assist rehabilitation robots based on human motion intention in recent years. This paper presents the various ways in which human motion intention in rehabilitation can be estimated. This paper also elaborates on the control laws for the estimation of motion intention of the power assist rehabilitation robot. From the review, it has been found that the motion intention estimation method includes: Artificial Intelligence-based motion intention and Model-based motion intention estimation. The controllers include hybrid force/position control, EMG control, and adaptive control. Furthermore, Artificial Intelligence based motion intention estimation can be subdivided into Electromyography (EMG), Surface Electromyography (SEMG), Extreme Learning Machine (ELM), and Electromyography-based Admittance Control (EAC). Also, Model-based motion intention estimation can be subdivided into Impedance and Admittance control interaction. Having reviewed several papers, EAC and ELM are proposed for efficient motion intention estimation under artificial-based motion intention. In future works, Impedance and Admittance control methods are suggested under model-based motion intention for efficient estimation of motion intention of power assist rehabilitation robot. In addition, hybrid force/position control and adaptive control are suggested for the selection of control laws. The findings of this review paper can be used for developing an efficient power assist rehabilitation robot with motion intention to aid people with lower or upper limb impairment.

The space station manipulator does lots of tasks with contact force/torque on orbit. To ensure the safety of the space station and the manipulator, the contact force/torque of manipulator must be controlled. Based on analyzing typical tasks’ working flows and force control requirements, such as ORU (orbit replacement unit) changeout and dual arm collaborative payload transport, an impedance control method based on wrist 6 axis force/torque feedback is designed. For engineering implementation of the impedance control algorithm, the discretization method and impedance control parameters selection principle are also studied. To verify the compliance control algorithm, a ground experiment platform adopting industrial manipulators is developed. In order to eliminate the influence of gravity, a real-time gravity compensation algorithm is proposed. Then, the correctness of real-time gravity compensation and force compliance control algorithm is verified on the experiment platform. Finally, the ORU replacement and dual arm collaborative payload transport experiments are done. Experimental results show that the force compliance control method proposed in this paper can control the contact force and torque at the end of the manipulator when executing typical tasks.

An intelligent rolling contact fatigue test equipment is developed, and the control methods are presented. For obtaining the slip accurately, the control method based on master-slave synchronization is proposed. For controlling the loads in high precision, the control method took into consideration the influence by two factors, displacement and the load. The nonlinear interference and excess torque in load control are effectively suppressed. Based on the SIMOTION D425 which is the Siemens integrated motion control system, the control system architecture of the intelligent rolling contact fatigue test equipment is constructed. The solutions of slip ratio and the experimental load controlled by these methods are satisfactory with the requirement of design precision. In the validation experiment, the load control accuracy is ±3%, the average error of load control is 1.77%, and the average error of slip control is 0.26%. The experiment results show the proposed control methods are feasible and effective.

The authors have studied on the positioning control of a cart by means of a smooth switching from the servo access control (SAC) for automatic conveyance function to the impedance control (IC) for power‐assisting function. The nonstationary optimal control (NOC) method and the force sensorless nonstationary impedance control (FSLIC) method were applied in a previous study. However, NOC requires the offline calculations for generating time‐varying feedback gains. This letter shows the experimental result of smooth switching from the adaptive nonstationary servo control (ANSSC) to FSLIC. ANSSC generates the feedback gains online and realizes some adaptive control for parameter variations of a controlled object. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.