CLOSED LOOP NONLINEAR OPTIMAL CONTROL OF A 3PRS PARALLEL ROBOT

Hami Tourajizadeh and Oveas Gholami

Keywords

3PRS parallel robot, optimal control, linear quadratic regulator(LQR), state-dependent Riccati equation (SDRE)

Abstract

Optimal regulation of a 3PRS parallel robot is performed in this article using closed loop methods. This robot is a three-DOF parallel robot with high stiffness useful for accurate applications. An accurate regulation of the robot using robust control while an objective function such as controlling effort could be minimized is highly necessary for employing the robot in high-precision ap- plication. In this article two main optimal controls of a linear quadratic regulator (LQR) and a state-dependent Riccati equation (SDRE) are designed and implemented on the proposed robot and advantages and disadvantages of each approach are analysed. A minimum amount of controlling effort is calculated for conducting a robust regulation process using a linear optimal control of LQR and a nonlinear optimal control of SDRE. To verify the optimality of the proposed optimal controllers of this article, their performance is compared with a simple regulator of PID. It is shown that using the proposed optimal and robust controllers, the desired set point can be achieved using a minimum amount of energy while the performance of the mentioned optimal controllers is also compared and analysed.

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