طراحي، شبيه‌سازي و پياده‌سازي روش‌هاي‌ كنترل ادميتانس و امپدانس روي يك واسط لامسه‌يي

Design, Simulation and Implementation of Admittance and Impedance Control Methods on a Haptic Device

در اين نوشتار به طراحي، شبيه‌سازي و پياده‌سازي چند كنترل‌كننده‌ي متفاوت روي يك واسط هپتيكي پرداخته شده و نتايج حاصل از اعمال اين كنترل‌كننده‌‌ها با يكديگر مقايسه شده‌اند. يك كنترل‌كننده‌ي امپدانس با بازخورد نيرو و يك كنترل‌كننده‌ي ادميتانس با بازخورد موقعيت روي اين واسط هپتيكي پياده‌سازي شده است. به‌منظور كنترل موقعيت در روش كنترل ادميتانس، از روش كنترل غيرخطي ديناميك معكوس استفاده شده است. در محل كارگير واسط هپتيكي از يك حس‌گر نيرو/گشتاور شش درجه آزادي براي افزايش عملكرد و پايداري واسط مورد نظر استفاده شده است. مقايسه‌ي نتايج حاصل از شبيه‌سازي و پياده‌سازي حلقه‌هاي كنترلي متفاوت حاكي از آن است كه پاسخ عملكرد روش كنترل امپدانس براي شبيه‌سازي ديواره‌ي سخت، و روش كنترل ادميتانس براي شبيه‌سازي ديواره‌ي نرم مناسب‌تر است. همچنين روش كنترل ادميتانس در كنترل واسط‌هاي هپتيكي با جرم و اينرسي بالا از عملكرد بهتري برخوردار است.

The lexical definition of haptic is of the sense of touch. Literally, it means the sensorial and force communication between the user and the virtual environment. A haptic interface is a means to receive the motion and sensed force from a human operator as its input, and lead the motion and force produced in the virtual environment back to the human operator. A haptic interface is commonly used in virtual reality systems and master/slave arms. Off-the-shelf haptic interfaces generally lack force sensors in their structures because of their heavy costs. As a result, the open-loop impedance is usually applied to control the haptic device. While the haptic interface is required to have light mass/weight, in order to reduce the dynamic effect on the function of the simulation, the more the mass is reduced, the less the interface can transmit the force. The goal of this paper is to investigate the design, simulation and implementation of different control algorithms on a haptic interface. In this study, impedance control with force feedback, and admittance control with position feedback, on a six degrees of freedom (DOF) haptic interface device, including three active and three passive DOF, are investigated. In admittance control, a nonlinear control algorithm with inverse dynamics is utilized. Furthermore, the kinematic and dynamic equations of the haptic device are derived. By employing a six degree of freedom force/torque sensor at the end-effector of the haptic device, the performance and stability of the system are improved substantially. Moreover, the proposed control algorithms are simulated in a MATLAB/Simulink environment to evaluate the effectiveness of the proposed control algorithm, prior to experimental implementation. Next, the results of simulations and implementations are compared. They imply that the impedance control algorithm has a better performance in hard virtual wall impact simulation, and the admittance control algorithm for soft virtual wall interaction. Further, the admittance control method shows better functionality compensating for the massive and high inertia of the haptic interface device. Finally, it is shown that system behavior improves in both approaches, while increasing the gain of the control loops.