Off-Line Optimal Trajectory Planning of a 6 DOF Robot Manipulator Using Multiple Objective Functions with Kinematic Constraints

Abstract

As robots are widely used in industries, it is important to improve their performance and accuracy of production process. This can be done by properly developing the trajectory planning process for the robot. Here a trajectory planning technique based on reduction of total operation time and total jerk is proposed. For this purpose, initially a 6 degrees of freedom robot is assumed.
Trajectory planning of robot manipulator is either offline type or online type. Offline trajectory planning means motion planning of the robot before applying it to the real world. Whereas online trajectory planning of robot manipulator means trajectory tracking and controlling during its operation. Here offline trajectory planning is used by considering kinematic parameters of the robot.
In the proposed trajectory planning process, initially it is considered that robot will follow a continuous path. Then the path is divided into few polynomial segments. During operation of the robot, as jerk is produced, it deviates the end-effector from its predefined path. So it is important to reduce jerk produced during operation of the robot. Hence here total operation time and total jerk value are considered to optimize. To reduce jerk it is important to ensure continuity of velocity and acceleration at each of the selected points. That is why cubic spline is selected. Deriving all equations, optimization is done by using sequential quadratic technique process.
Here MATLAB R2015a is used for all calculations and plotting. Results obtained after optimization are compared with results before optimization. It has been found that the total operation time is significantly reduced. Jerk produced before optimization and after optimization are compared via graph. Total jerk value is also found to be reduced after optimization.