Reduced Voltage Control of Electrically Driven Flexible-Joint Robot Manipulator Based on Model Predictive Method

In this paper is proposed a new approach to controlling a flexible-joint robot manipulator based on a predictive controller and voltage control strategy in the presence of external disturbances. In this approach is used a 2DSFJ[1] Robot for modeling, design, analysis, and simulation.  The controller design is done once with feedback from all system states (main controller) and again only with feedback of the motor position (reduced controller), which in this case, some hardware equipment will be eliminated. The designed controller will have the advantages of predictive control method and voltage control strategy at the same time. So, in addition to simplicity, the control law has an independent joint structure. Also this approach resolves the limitations of the torque control strategy, such as the high computational volume, ignoring of the actuators electrical dynamics, and implementation problems. The prominent features of the proposed approach as follow: online optimization of the voltage control signal, design of predictive controller based on voltage strategy and controller order reduction. Other advantages of this approach include: simplicity in design and proof of stability, flexibility in tuning the sampling time and predictive control horizon, consideration of system input and output limitations in the voltage control law, good disturbance rejection, and improved performance of closed-loop system. In order to analyze the performance of the proposed approach, stability analysis of control system for both main and reduced controllers was performed by Lyapunov-based method, and computer simulation in problem of regulation and tracking of the reference signal along with increasing and decreasing its frequency for evaluating the response speed, and adding external disturbance by using the main and reduced controller will be done. Also, the advantages and limitations of the presented approach in terms of hardware and controller performance are analyzed by comparing the results of the simulations with other papers, and thus the stability of the closed-loop system and its proper performance is guaranteed.