PID Sliding Mode Control of Prolate Flexible Pneumatic Actuators

Abstract

The inherent compliance, high power-density, and musclelike properties of soft actuators are especially attractive and useful in many applications, including robotics. In comparison to classical/modern control approaches, model-based control techniques, e.g., sliding mode control (SMC), applied to flexible fluidic actuators (FFAs) offer significant performance advantages and are considered to be state-of-the-art. Improvements in position tracking are possible using nonlinear control approaches that offer enhanced performance for common applications such as tracking of sinusoidal trajectories at high frequencies. This paper introduces a SMC approach that increases the tracking capabilities of prolate flexible pneumatic actuators (PF-PAs). A model-based proportional, integral, derivative sliding mode control (PIDSMC) approach designed for position control of PFPAs is proposed. SMC and PIDSMC systems are implemented on low-cost open-source controls hardware and tested for tracking sinusoidal trajectories at frequencies of 0.5 Hz and 1.0 Hz with an amplitude of 8.255 mm and an offset of 12.7 mm. The PIDSMC approach reduced the maximum tracking error by 20.0%, mean error by 18.6%, and root-mean-square error by 10.5% for a 1 Hz sinusoidal trajectory and by 8.7%, 14.7%, and 3.8%, respectively, for a 0.5 Hz sinusoidal trajectory. These reductions in tracking errors demonstrate performance advantages of the PIDSMC over conventional sliding mode position controllers.

Robust Control Law for Pneumatic Artificial Muscles

“…Research suggests that a third-order lumped parameter model can predict the dynamic behavior of a PAM [32]. However, valves that are not high performance or long pneumatic lines can make this third-order model insufficient.…”

“…wheref andĝ are model estimation parameters determined by solving for control input in the third order model, similar to those presented in [23] and [32]. With a Lyapunov like function, 1 2 d dt s 2 ≤ −η | s |, the robust control law is determined to be…”

Sliding Mode Impedance Control of a Hydraulic Artificial Muscle

“…Extensive control development for PAMs has been reported for several decades [13][14][15][16][17][18][19][20][21]. Most notable are the model-based sliding mode controllers (SMC) that improve control performance and are inherently robust with accuracy of 15 µm reported [14-16, 20, 22].…”