Active Compliance Control on the Hydraulic Quadruped Robot With Passive Compliant Servo Actuator

Abstract

A hydraulic servo actuator with passive compliance (HPCA) is designed for hydraulic actuated quadruped robots, aiming to solve the response discrepancy of the low-bandwidth servo valve to impact forces between robot's feet and the ground. This paper focuses on the performance of this passive compliance method combined with an active compliance control strategy when used on quadruped robots. First, the frequency-response characteristics of the HPCA are further discussed. Then, combined with the requirements of the quadruped robot, a compliant method characterized by incorporating dynamic feedforward control and joint angle feedback control items into the virtual model is proposed. Finally, both the new algorithm and the performance of the HPCA are verified by simulation and experiment. The results demonstrate that, compared with the original actuator, the frequency-response characteristics of the HPCA have better adaptability for the quadruped robot, while the efficiency of the active compliance control is also improved by this novel passive compliance strategy.

A hydraulic actuator for joint robots with higher torque to weight ratio

“…The phase difference in the retraction direction is larger than that in the extension direction, which is caused by the difference between K rq and K lq in Eq. (19). When a phase difference is not considered, the amplitude tracking error is very small, 0.8% at 0.5 Hz, 1% at 1 Hz, and 1.5% at 2 Hz.…”

“…( 21) has similar properties to Eq. (19). In other words, we can design similar control algorithms for the position control and torque control for the HyA as:…”

“…It is worth noting that at present, HyAs that can directly convert the liquid pressure and flow of hydraulic oil into the output mechanical rotary motion and torque do so in the form of vanes [13][14][15]. Other forms of lightweight rotary HyAs have been studied from many aspects [16][17][18][19][20][21], but they essentially convert linear motion and force into output rotational motion and torque through specific mechanisms [22,23].…”

Modeling and analysis on low energy consumption foot trajectory for hydraulic actuated quadruped robot

“…According to equation ( 5), load forces (f l Þ acting on each hydraulic actuators must be calculated so as to obtain the energy consumption model of SCalf-II. To meet the demand of high dynamic performance, the constant pressure system is always adopted in hydraulically actuated quadruped robots, such as Scalf-II which was designed in 2012 for orientation in rough terrain, 22 as shown in Figure 2.…”

Analysis and Optimization of Interpolation Points for Quadruped Robots Joint Trajectory

“…Semini et al added the foot speed in the flattened part of the semi-ellipse to coordinate the forward speed of the trunk during the trot motion [11]. Rong et al used a compound trajectory consisting of cubic curves with straight lines on their Scalf robot [12] and demonstrated a foot-end trajectory consisting of five-degree polynomials with four-degree polynomials in Scalf afterward [13]. For more flexibility, the researchers of MIT used the Bézier curve in its MIT Cheetah [14], which utilized twelve position control points for the foot-end trajectory and connected them with eleven-degree Bernstein polynomial curve.…”