This paper aims to improve the energy autonomy and the mechanical performances of an on-board drive chain for robotics. The energy autonomy improvement is performed by reducing electrical losses in the inverter. Electrical losses are reduced by decreasing the number of switching cycles per period of the inverter’s power semiconductor switches, while maintaining a low Total Harmonic Distortion (THD). These improvements are expected thanks to a new control strategy called Pre-Calculated Pulse Width Modulation (PC PWM). The principle of this new control strategy is that all the symmetries of an ideal three-phase voltage system are assigned to the real output voltage of the inverter. Then the switching instants of the inverter’s switches are determined off line, by means of Fourier’s analysis, so that the maximum number of successive harmonics is zeroed. This allows the optimal switching sequence to be predefined, thereby reducing unnecessary commutations of the power switches. The performance of the new method (PC PWM) is evaluated through detailed simulation studies and compared with the conventional method called Sinusoidal Pulse Width Modulation (SPWM). The simulation results show that despite the reduction in the number of commutations per period, the performance of the actuation chain has been significantly improved with PC-PWM (new technique). Indeed, for the same mechanical load, the PC-PWM method allows for a lower current, a shorter transient response time and a lower torque ripple than the SPWM method.

Stroke survivors with spasticity, an involuntary increase in muscle tone, often struggle to access specialized equipment and medical support for their rehabilitation. Rehabilitation exercises are daily routines requiring patients to perform repetitive movements of their spastic joints. To reduce patient mobilization within hospitals, offering orthoses suitable for use in home settings, outside of clinical environments, is required to limit the involvement of healthcare personnel in the treatment of hemiparesis for patients. Such orthoses must be designed to be portable and be able to tolerate the erratic motions of spasms without breaking or injuring patients. This paper presents the use of magnetorheological actuators to design an elbow orthosis, improving weight, reactivity, and transparence necessary for effective rehabilitation of spastic patients. A prototype is designed, built, and characterized experimentally. Results suggest that the technology is lightweight and highly transparent to erratic motion, and thus well-suited for spastic patients.