A Modular and High-Precision Motion Control System With an Integrated Motor

Abstract

Abstract-This paper describes the design and control of an integrated direct-drive joint suitable for applications that require a high-precision motion control system. The joint integrates a directdrive synchronous motor with axial air gap, a torque sensor, and a high-resolution position sensor. The key design aspects of the integrated joint, like the motor's armature, cooling system, motor housing, bearing arrangement, sensors, and power electronics are detailed. We also present a number of advanced implementations in motor torque control, optimal joint torque sensory feedback, and motion control using positive joint torque feedback. Experimental results illustrate an outstanding performance regarding thermal response, torque ripple, reference trajectory tracking, torque disturbance rejection, and joint stiffness.

Energy-Efficient and Fault-Tolerant Control of Multiphase Nonsinusoidal PM Synchronous Machines

“…The back-EMF waveforms are measured by using the hydraulic dynamometer [52]. Knowing that the per-phase back-EMF function and torque function have the same waveshape dictated by the airgap flux density, the back-EMF function is experimentally identified by measurement of the torque produced by individual motor phases at different mechanical angles.…”

Design and Comparative Analysis of a Retrofitted Liquid Cooling System for High-Power Actuators

“…This is a central consideration for any high-performance motor design and is often addressed either by using forced convective air cooling [1] or by adopting liquid cooling [10,12,18]. Table 1 demonstrates the benefits of liquid cooling with water, where water exhibits up to a 50× improvement in convective heat transfer compared to air.…”

“…Existing work can be largely grouped into two distinct categories, each benefiting from the increased continuous torque production. The first category applies liquid cooling to direct drive robotic joints [15][16][17][18]. Drivetrains introduce cost, complexity, additional points of failure and can significantly reduce system efficiency (beyond 50% in some cases [19]).…”

“…By liquid cooling a direct drive motor, this torque/mass drawback is reduced. In one study, the continuous torque improved by a factor of six when liquid cooling was applied, resulting in a overall torque/mass of 15 Nm/kg [4,18]. Unfortunately, such motors require a completely custom design and many years of iterative development to obtain a reliable device.…”

Guest Editorial Introduction to the Focused Section on Electromagnetic Devices for Precision Engineering

“…Aghili et al [43] presented an integrated direct-drive system for high-precision motion control. The torque, motion and feedback aspects were addressed in the work.…”