This paper suggests an inverse optimal PID control design method to track trajectories in Lagrangian systems. The inverse optimal PID controller exists if and only if the Lagrangian system is extended disturbance input-to-state stable. First, we find the Lyapunov function and the control law that satisfy the extended disturbance input-to-state stability by using the characteristics of the Lagrangian system. The control law has a MID control form and satisfies the Hamilton-Jacobi-Isaacs equation. Hence, the H/sub /spl infin// inverse optimality of the closed-loop system dynamics is acquired through the PID controller if the conditions for the control law are satisfied. Also, simple coarse/fine performance tuning laws are suggested based on a performance limitation analysis of the inverse optimal PID controller. Selection conditions for gains are proposed as functions of the tuning variable. Experimental results for a typical Lagrangian system show that our analysis provides performance and H/sub /spl infin// optimality.
Despite recent significant advances in technology and medicine, the number of patients who undergo amputation of body parts for various reasons continues to increase. Assistive devices such as prosthetic arms can enable limited activities in upper limb amputees and improve their quality of life. This study aims to help in the development of user-centered prosthetics by identifying user requirements and key considerations during selection of prosthetics. This study conducted a questionnaire survey after obtaining prior consent for persons with disabilities with upper limb amputation who visited orthosis companies, rehabilitation centers for the disabled, veteran’s hospitals, and labor welfare corporations. A modified questionnaire was conducted to upper limb prosthetic users and results were analysed using descriptive statistics and t-test. Results of the study showed that the main reasons for discontinuing the use of prosthetics were discomfort (discomfort in wear, weight, and difficulty of detachment) and complaints regarding design and function. Regardless of the prosthesis type, the color and design of the prosthesis were key considerations in prosthesis choices. Respondents indicated that they needed various prostheses designed according to the purpose and situation, such as for sports like golf and cycling as well as everyday use. Most of the respondents answered that buttoning shirts, tying knots, and using chopsticks were challenging or impossible to do on their own. Based on the results of this study, the quality of life of upper limb amputees can be improved if a prosthetic arm with various functions that can satisfy both the user’s needs and wants is developed.
An optimization-based real-time joint angle extraction method of human elbow is proposed by processing the biomedical signal of surface EMG (electromyogram) measured at the center point of biceps brachii. The EMG signal is known as non-stationary (time-varying) signal, but we assume that it is quasi-stationary because a physical or physiological system has limitations in the rate at which it can change its characteristics. Based on the assumption, a pre-processing method to obtain pre-angle values from raw EMG signal is firstly suggested, and then an optimization method to minimize the error between the pre-angle and real joint angle is proposed in this paper. Finally, we suggest the experimental results showing the effectiveness of the proposed algorithm.
This paper presents an underactuated finger mechanism enabling both self-adaptive grasping and natural motion such as flexion and extension. It has three degrees-of-freedom mechanism composed of one actuator and a couple of passive components including torsional springs and mechanical stoppers. In detail, the proposed mechanism consists of two five-bar and one four-bar linkages. Since each five-bar linkage contains passive components, it is allowed to have adaptive grasping as well as natural motion for human finger-like behavior. Kinematics and static force analysis are performed to reveal the operational principle of the proposed mechanism. Finally both simulation and experiments are conducted to show the design feasibility of the proposed mechanism.
The PID (proportional-integral-derivative) state observer to make an output feedback PID controller is suggested for robotic systems. When an inverse optimal PID controller (full state feedback one) is utilized with this PID state observer, an output feedback PID control system recovers the extended disturbance input-to-state stability (ISS) of a full state feedback PID control system, if only one condition for an observer gain parameter is satisfied. The condition is derived from the stability proof and it depends on only the proportional gain value among the gains in the PID controller
A systematic procedure is developed for the design of new adaptive robust torque tracking control for electro-hydraulic actuators with both parametric uncertainties and uncertain nonlinearities such as frictions. The dynamics of the electro-hydraulic actuators is assumed to be linearly parameterized about model parameters to develop the adaptive and robust control. The proposed algorithm is composed of the adaptive part for dynamic compensation and the robust part for overcoming the error of the estimated nonlinearities. The adaptation law is based on the previous Lyapunov analysis and the robustness to uncertain nonlinearities is obtained by a L 2 -gain analysis for disturbance attenuation, which does not require the knowledge of the bound of the disturbance. There are two main advantages of the proposed algorithm which become significant during implementation. One advantage is that the accurate dynamic compensation is realized for the torque tracking. A second advantage of this method is that the uncertain nonlinearities, which is difficult for the use of the adaptation law, are considered and compensated for with the robust control using L 2 -gain analysis. The controller shows the tracking accuracy in presence of both parametric uncertainties and uncertain nonlinearities.
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