DC Servo Motor Drive for 6DOF motion Platform

Abstract: This project details the design and implementation of custom DC servo motor drives for a 6DOF motion platform used in ineractive simulators. The challenge arose from the obsolescence of the original motor drives, rendering replacement parts unavailable. This in-house solution ensured compatibility with the existing platform while offering improved performance.

Challenge:

A client utilizing our 6DOF motion platform encountered a critical issue due to the failure of the obsolete motor drives. Replacing these drives with new, commercially available options was not feasible due to incompatibility with the existing system.

Requirements:

The custom DC servo motor drives needed to meet the following specifications:

• Control Modes: Support for Torque, Position, and Speed control modes
• Compatibility: Seamless integration with the existing 6DOF platform
• Motor Rating: Ability to drive 1.2KW permanent magnet DC (PMDC) motors

Solution:

As the lead design engineer, I spearheaded the development of the motor drive circuit. The design utilized Intelligent Power Modules (IPMs) for efficient motor control. These modules incorporated Hall effect-based current sensors, providing accurate current measurement with inherent isolation. The control circuit employed a popular microcontroller based on the ARM Cortex M3 architecture.

To address the limitations of the existing 8-bit encoder, an extended high gain observer was implemented. This technique effectively reduced quantization error, resulting in improved control performance. Our research on this topic has been published in a peer-reviewed paper ([link to research paper, https://ieeexplore.ieee.org/document/7162442]).

Impact:

Despite the limited team size, the project delivered a high-performance motor drive solution comparable to those developed by larger engineering teams. This not only enabled us to continue utilizing the existing 6DOF platform, saving significant costs, but also fostered valuable in-house expertise in the crucial field of motor drive design, paving the way for future development of custom motor drives for new motion platforms.