This Small Business Innovation Research (SBIR) Phase-II research project aims to cut the manufacturing cost of an innovative power-efficient ultra-miniature, brushless-servo-electronics module from $1,000 to $100. The module integrates all rotor-position sensing, vector-based commutation, controls, and power supplies needed to drive high-performance brushless servomotors rated up to 300 W (Root Mean Square) and 2 KW (peak) into a single 50-gram module not much bigger than a bottle cap. The cost reduction relies on a set of innovations led by replacement of laser optics used for rotor-position sensing with an array of magnetic field sensors measuring a calibrated target magnet. Phase I demonstrated that well-placed shielding enables high precision and excellent commutation performance even in the proximity of stray fields produced by high switched currents and spinning rotor magnets located in the motor body only millimeters from the sensor array.
This servo-electronics module fits the definition of disruptive technology for entrenched players, such as Danaher/Kollmorgen, Siemens, Fanuc, and Yaskawa, while it will enable scores of original equipment manufacturers (OEMs) to improve the performance, compactness, power efficiency, and reliability of their machines at competitive prices. As machines become more intelligent through embedded processing and sensor fusion it will improve not only industrial productivity, but quality of life as society ages. While embedded processors and MEMS-based sensors have become tiny, highly effective, and affordable, similar improvements in servomotors have evolved more slowly. At fractional-horsepower levels the power electronics contribute significantly to total motor-system bulk and complexity. Providing smaller and more efficient servo-electronics will enable OEMs to increase the competitiveness of their products. Robots will become more agile with additional degrees of freedom and less mass to accelerate.
This Small Business Innovation Research (SBIR) Phase II and IIB project leveraged previous government-funded work and enabled Barrett Technology to introduce its 35-mm-diameter Puck™ motor controller and amplifier with embedded magnetic encoder. This module is used in Barrett’s two flagship products: the 7-Axis WAM™ Robot Arm (8 Pucks per system), and 3-fingered BarrettHand (4 Pucks per system). With this funding, Barrett has also developed a 19-mm-diameter model with near-equivalent specifications and is in the process of commercializing this technology. Barrett also employed 6 high-school and college students as interns performing challenging and useful engineering work in the engaging field of robotics. Unique to the Puck-family of products is the large feature-set and performance ranges relative to physical size. The Barrett Puck is a networkable brushless motor amplifier with embedded encoder and precision current sensing that can control the torque output of brushless motors with state-of-the-art space vector commutation and very low torque ripple. The Puck operates at any bus voltage between 18-60 VDC without reconfiguration and will command a smooth, continuous torque even when the input voltage is varying. It offers several analog and digital input/output connections allowing for additional sensors and small actuators. The Puck was designed to replace standard motor encoders and can be placed directly on the back of a motor. By combining the power electronics, position encoder, communication circuitry, and control intelligence in a small and sealed package, Barrett has been able to design its robot products with a distributed architecture and minimal system wiring. With additional and continuing commercialization efforts, Barrett will be enabling other companies to do the same.
