Introduction of a redundant actuator using planetary gear trains for human centred robotics

Abstract

Matching motor efficiency and performance with the load demands can significantly improve the overall efficiency of a driveline. Inspired by the automotive sector -with the high interest of hybrid and electric cars currently-, the authors have studied how state of the art technologies can be used in the relatively new field of collaborative and Human centred robotics. Multiple transmission systems have been considered, among others redundant actuators (both static and kinematic) and continuously variable transmissions. Based on these findings and the experience of the research group on customised planetary gear trains for Human Limb Assistance and Replication, an extensive review of existing redundant actuators is presented in combination with an alternative transmission system which does not need any auxiliary gear transmissions and hence can be lighter and more compact than state of the art drivelines for Human centred robotics. A calculation was performed -including the efficiency model presented by Müller- which shows the high potential of this type of dual-motor actuator.

Torque method investigation of wolfrom gear trains

“…The most commonly used reduced PGTs are the Wolfrom and Ravigneaux gear trains. Due to its large transmission ratio and compactness, the Wolfrom PGT [9] is used in some special cases in which its low efficiency is not a problem -in low-power transmissions in robotics, for example [10], [11], or in mechanisms with noncontinuous operation (travel mechanism of handling machines, for example) [1], etc. [12], [13].…”

Dual-Motor Planetary Transmission to Improve Efficiency in Electric Vehicles

“…subject to the constraints expressed by Equations ( 2) and ( 4). In order to find the best solution, a genetic algorithm (GA) is adopted that is one type of global, derivative-free, and stochastic approach widely used to solve optimization problems in the design of electric vehicles [24]. The GA algorithm keeps a random population of N individuals (here 25), each defining a speed ratio i in the range of interest [0, 100].…”

“…During normal operations, the ring gear velocity is determined by the vehicle speed, while the first motor speed can be controlled with the aim to keep the combustion engine in its best efficiency window. Other recent applications can be found in robotics, where the use of multiple motors for a single revolute joint is evaluated in [23], whereas a customized planetary gear train for human limb assistance and replication is discussed in [24]. Here, we investigate the use of a planetary gear for the power transmission of full electric vehicles with the aim to uncouple the speed range of two electric motors from that of the car and keep both electric machines in their optimal efficiency window.…”