Nonlinear Control For Asymptotic Regulation Of Flexible-Joint Robots

It is well known that the joint flexibility must be considered to achieve better link control performance. However, the consideration of joint flexibility may lead to very complex control system.A detailed analysis of the joint flexibility is given in this paper and a new class of proportional plus nonlinear derivative control with desired gravity compensation (P-ND+) for flexible joint robots is proposed to give a faster response and higher position control precision over the commonly used control strategies. The proposed P-ND+ control eliminates the vibration in industrial robot manipulators which is due to the presence of joint flexibility. Furthermore, a class of proportional plus plus nonlinear derivative control with real-time gravity compensation (P-ND) is proposed to achieve a much improve control performance.In practice, velocity measurements are prone to be contaminated by noise and degrade the performance of the controller. To overcome this problem, in this paper, a new output feedback PD (OPD) controller for position control is developed for flexible joint robots without velocity measurements. In addition, to improve the control performance further an output feedback proportional plus nonlinear derivative control (OP-ND) with real-time gravity compensation is proposed. The proposed OP-ND is formulated with a class of nonlinear saturated function with the characteristics of'enlargement of small error and saturated in large error'.At last, taking into account the requirements of engineering a saturated input constrained PD control with real-time gravity compensation (SPD) and an output saturated PD with control (OSPD) are proposed. Both the two proposed control algorithms achieve good control performance in the presence of actuator constraints。...