Highly integrated, radiation-hardened, motor controller with phase current measurement

Abstract

Robotic systems provide an excellent on-site or remote support for astronauts during routine tasks and perform increasingly complex autonomous tasks during exploration missions. New systems like the robotic arm CAESAR and the highly dexterous four fingered robotic hand Spacehand are designed in order to improve the skills and performance of the systems while the needed space for the electronics and the power consumption is decreasing. The small exploration systems MASCOT highlighted the need for a small form factor, highly integrated, lightweight but simultaneously a highly performance motor controller. This paper presents a cold redundant, three phase brushless DC motor driver for medium radiation environment which was developed at the Robotics and Mechatronics Center of the German Aerospace Center (DLR-RMC). The size efficiency of the proposed design relies on an extremely compact position sensing circuit which is based on a resolver principal. The integrated bridge driver, with current limitation, withstands a continuous power up to 120W. To simplify the design the internal voltages are limited to a minimum set. A fault-tolerant processor is used to guarantee a high reliability, The choice of several standard communication interfaces gives the user multiple possibilities to integrate the board in existing designs. The small form factor improves and simplifies the thermal management as well as the integration in small systems. The simple mechanical shape reduces the integrator effort and offers a large amount of configurations. The three phase current sensing, together with the high performance computation platform, allows the implementation of a high level current control such as field oriented control methods. Such control methods optimize the dynamic performance of the actuator, thus, leveraging the actuator performance to size ratio. The system uses a fully programmable processor unit, offering real-time communication and logging capabilities, fully integrated control loops and rich monitoring. This paper gives an overview of the requirements, discusses several of the keys aspects of the design and reports the current state of the design.