Nonlinear optimal control for a 4-DOF SCARA robotic manipulator

Abstract

Selective compliance articulated robot arms (SCARA) robotic manipulators find wide use in industry. A nonlinear optimal control approach is proposed for the dynamic model of the 4-degrees of freedom (DOF) SCARA robotic manipulator. The dynamic model of the SCARA robot undergoes approximate linearization around a temporary operating point that is recomputed at each time-step of the control method. The linearization relies on Taylor series expansion and on the associated Jacobian matrices. For the linearized state-space model of the system, a stabilizing optimal (H-infinity) feedback controller is designed. To compute the controller’s feedback gains, an algebraic Riccati equation is repetitively solved at each iteration of the control algorithm. The stability properties of the control method are proven through Lyapunov analysis. The proposed control method is advantageous because: (i) unlike the popular computed torque method for robotic manipulators, it is characterized by optimality and is also applicable when the number of control inputs is not equal to the robot’s number of DOFs and (ii) it achieves fast and accurate tracking of reference setpoints under minimal energy consumption by the robot’s actuators. The nonlinear optimal controller for the 4-DOF SCARA robot is finally compared against a flatness-based controller implemented in successive loops.

Intelligent Logistics Handling Robot: Design, Control, and Recognition

“…SCARA robotic arms are usually characterized by high accuracy, high speed and repeatability [2], [3]. In this project, the SCARA robotic arm is designed as a threedegree-of-freedom, containing one rotational degree of freedom in the XY plane, one lifting degree of freedom in the Z-axis, and one moving degree of freedom in the Z-axis.…”

“…The process of solving the operational science model of the three-axis SCARA robotic arm is as follows: Determination of joints, connecting rods and their parameters. The robot arm uses a rotating chassis at the bottom, lifting and lowering using a stepper motor screw Z-axis, and a rotating arm in the XY plane, for a total of three degrees of freedom, and the analysis process is simplified by dropping the end-effector [3].…”

“…The intelligent logistics handling robot studied in this project comprehensively designs and analyzes aspects such as mechanical structure, robotic arm control and coordinate calculation, chassis control and global positioning, image recognition, and processing. A multifunctional intelligent logistics handling robot (AGV) is designed based on the omnidirectional wheel structure chassis and planar articulated (SCARA) robotic arm [1], [2], [3], [5]. It integrates functions such as positioning, environmental perception, path planning, material recognition and grasping, material placement, and stacking.…”