Non-overshooting force control of series elastic actuators

Official URL: http://dx.doi.org/10.4028/www.scientific.net/SSP.166-167.421

Whenever mechanical devices are used to interact with the environment, accurate control of the forces arising at the interaction surfaces arise as an important challenge. Traditionally, force controlled systems utilize stiff force sensors in the feedback loop to measure and regulate the interaction forces. Series elastic actuation (SEA) is an alternative approach to force control, in which the deflection of a compliant element (orders of magnitude more compliant than a typical force sensor) placed between motor and the environment is controlled to regulate the interaction forces. The use of SEAs for force control is advantageous, since this approach possesses inherent robustness without the need for high-precision force sensors/actuators and allows for accurate control of the force exerted by the actuator through position control of the deflection of a compliant coupling element. Here, a non-overshooting force controller is proposed to be embedded into the control structure of SEAs. Such a controller ensures safe operation of the SAE by making sure that the force applied to the environment is always upper bounded by the reference forces commanded to the controller.