Abstract
This paper presents a simple approach to building a robotic control system. Instead of a conventional control system which solves the inverse kinematics in real-time as the robot moves, an alternative approach where the inverse kinematics is calculated ahead of time is presented. This approach reduces the complexity and code necessary for the control system. Robot control systems are usually implemented in low level programming language. This new approach enables the use of high level programming for the complex inverse kinematics problem. For our approach, we implement a program to solve the inverse kinematics, called the Inverse Kinematics Solver (IKS), in Java, with a simple graphical user interface (GUI) to load a file with desired end effector poses and edit the configuration of the robot using the Denavit-Hartenberg (DH) convention. The program uses the closed-loop inverse kinematics (CLIK) algorithm to solve the inverse kinematics problem. As an example, the IKS was set up to solve the kinematics for a custom built serial link robot. The kinematics for the custom robot is presented, and an example of input and output files is also presented. Additionally, the gain of the loop in the IKS is optimized using a GA, resulting in almost a 50% decrease in computational time.
Highlights
Ordinary control systems for robots are based on having a controller which continuously calculates the inverse kinematics for the robots [1,2]
We present a new approach, where the inverse kinematics is solved ahead of time
There will probably be a shift towards offline programming, even for smaller businesses. This can reduce the time for reprogramming and re-purposing of robots while the robots are still producing. Considering that it takes 400 times as long to program a robot for a complex task as it takes for the robot to perform that task [4], offline programming can be a valuable tool for reducing Life-Cycle Cost (LCC) and increasing Overall Equipment Effectiveness (OEE)
Summary
Ordinary control systems for robots are based on having a controller which continuously calculates the inverse kinematics for the robots [1,2]. Similar to offline programming of robots, the inverse kinematics is solved before the robot performs its task. This approach reduces the complexity of robot control system tenfold, resulting in a system that only needs to read joint values from a file and send the values to the actuators of the robot with a given cycle time. For many of the applications of robots where the programming is performed offline, the tasks are performed without external feedback This opens up the possibility of pre-calculation of the inverse kinematics.
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