RETRACTED: Double speed loops control for high-precision position tracking of position-controlled actuators involving a harmonic drive reducer

Abstract

In this article, a kind of position control method based on double speed closed loops is proposed to reduce turning error and nonlinear dead zone, which are caused by the flexibility and nonlinear friction in harmonic drive system. The speed loop of motor side is the inner loop and the speed loop of load side is the outer loop. Besides, the robustness performances of double speed loops and single speed loop are analyzed in theory, respectively. And it is stated that the performance of double speed loops is better than the performance of single speed loop. Furthermore, to further reduce the turning error and enhance the precision of system, the article puts forward applying double proportional-integral controllers with double extended state observers in the two speed loops. Extended state observers can transform the nonlinear models into an approximate linear model and eliminate the nonlinear frictions in the system. Finally, a few comparative experimental results show that the proposed control method has better performance for restraining the nonlinear features and enhancing the precision of the harmonic drive system.

Feed-forward control of elastic-joint industrial robot based on hybrid inverse dynamic model

“…As the fourth derivative of the link error is much larger than the second or third derivatives, the terms, 2 _ M : : : e and € M€ e are negligible compared with Me (4) for a typical motion. 20 Therefore, the equation ( 38) is written as By applying equations ( 37) and (39) to equation (36), the following equation can be obtained,…”

“…The existence of flexible robot joints also makes the high-performance control of robot very complex and difficult. In Cai et al, 20 a kind of position control method based on double speed closed loops for elasticjoint robot is proposed to reduce turning error and nonlinear dead zone. This control method is pure feedback control so that the improvement of control performance is limited.…”

Velocity Estimation Methods with Applications to Tracking Control of a Harmonic Drive System

“…One subsystem model describes the actuator/motor side whereas the other describes the load side. For a harmonic drive system, Cai et al proposed a control scheme with double speed loops, consisting of one speed loop for the motor side and the other for the load side (4,5) . Moreover, the speed loop for the motor side is an inner loop whereas the speed loop for the load side is an outer loop.…”