Introduction

In this project, the design of ABB's IRB 360 from the FlexPicker series was utilized as a reference for implementing a servo drive with a microcontroller for an industrial delta parallel robot. Figure 1 provides an overview of the general configuration and dimensions of the IRB 360 model.

Top View

Front View

$$ \text{Figure 1} $$

Code Repository

The Arduino code for this project is available at the following GitHub link.

https://github.com/MinThihaSoe/Delta-parallel-Robot

Workspace

Unlike serial robots, computing forward kinematics in parallel robots like the delta robot involves complex geometric arguments tailored to each specific robot. For example, in the IRB 360 delta robot, forward kinematics are determined by the intersection point of three spheres originating from the base link's distal ends, as detailed by Gafford (2014). Appendix section 1 contains the equations used to calculate the robot's workspace. Based on Liu et al.'s paper (2019), the angle between the base's x-y plane and the actuating link typically ranges from -40° to 80°, where angle is positive at negative z axis. With the information provided in the IRB 360 datasheet, the workspace can be plotted as shown in figure 2.

$$ \text{Figure 2} $$

Pick-and-place path planning

After determining the workspace, a simple pick-and-place operation can be achieved by selecting four arbitrary points within the workspace and implementing a waypoint tracking PD controller. To simplify the problem, all points are chosen to lie along the x = 0 axis. The origin and pick location are set at ( 300, -800) in the y-z plane, respectively. The end-effector is then programmed to move upward to -700 along the z-axis and traverse horizontally along the y-axis until it reaches -300. Subsequently, the end-effector is planned to move vertically until it reaches -800 along the z-axis, which is designated as the final placement location. Figure 3 illustrates the gate shape trajectory path that is set to achieve in this project.

$$ \text{Figure 3} $$

Implementation

The implementation and testing of the servo drive for the delta robot with Arduino initially started with component selection. A potentiometer was chosen as the position sensor for the stepper motor, enabling feedback control. To facilitate this setup, mounts for both the motor and potentiometer were 3D printed. Additionally, 5mm to 8mm aluminum couplings were acquired to ensure proper mechanical connection between the motor shaft and the sensor. The list of components shown in Table 1 were integrated to enable the testing and validation of the servo drive functionality for the delta robot.

Circuit setup