Motor Characterization for Small Running Robots (2016)

This is an experimental comparison of small hobby brushless motors to evaluate their suitability as actuators for dynamic, small running robots. The work argues that cheap RC-style brushless motors offer excellent power and low mass but are poorly matched to available controllers for torque-controlled, bursty demands of running robots. Basic motor theory is used to justify selecting "pancake" geometries for torque density, and a simple bench protocol measures line-to-line resistance and back-EMF (using a drill to spin the motors) to compute torque constant (Kt) and motor constant (Km = Kt/√R). The write-up also inspects construction details - lamination thickness, magnet quality, winding neatness, bearings and axial retention - to judge mechanical adaptibility.

Six motors are teardowned and quantified: Turnigy HD 5208 Gimbal, Turnigy Multistar Elite 5010, Gartt ML 5208, Turnigy Multistar 4830, Turnigy Multistar 4822, and Flycat i-Rotor 5010. Results show a wide spread: the HD 5208 yields a very high torque constant (0.3081 N·m/A) but enormous winding resistance (11.7 Ω) and large mass, while the Multistar Elite 5010 posts the best motor constant (~0.093 N·m/√W) with low resistance and clean construction. Gartt and the Multistar 4830/4822 sit below that, and the cheap Flycat performs predictably worse. Conclusion: hobby brushless motors can be promising for small robots if paired with controllers that allow aggressive, dynamic current limits and if mechanical adaptations address bearing/shaft and mounting differences.