Abstract
In order to meet the requirement for the real-time of the hydraulic walking robot (WLBOT) and the stability of its movement, an embedded controller is proposed, which takes charge of multi-sensor information processing and signal output of the servo valve. The controller is capable of receiving control command and sending processed information while communicating with an embedded single board computer PCM-3365 via Control Area Network (CAN) bus at a 200 Hz frequency. In this paper, an appropriate interrupt cycle is selected and a 2 kHz high-speed control loop is run after we research the relationship between analog-to-digital converter direct memory access (ADC–DMA) interrupt cycle, data volume, and sampling rate. Significantly, the control strategy of WLBOT joint is introduced and a proportional-integral-derivative (PID) compound controller with velocity feedforward compensation (VFC) is realized. Meanwhile, the Chebyshev filtering algorithm is utilized to attenuate the vibration noise of joint signals. What’s more, an impedance controller is designed to gain better locomotion behavior and compliance in joint force control. Finally, the joint angle tracking and robot walking experiments are implemented, where the feasibility of the design and the validity of the control algorithm is verified. The results show that the PID velocity feedforward compensation controller can reduce the maximum tracking error by 39.13% and 71.31% in the knee and hip joint and the impedance control can reduce the standard deviation (SD) of the foot force by 36.06% and 72.79%.
Highlights
Over the past decades, multilegged robots have gained more and more attention for their ability to traverse nonstructural environments and uneven terrains like mammals or insects
Due to the existence of interrupt nesting, we introduce a temporary storage array in analog-to-digital converter direct memory access (ADC–DMA) interrupt service routine (ISR) to reduce the impact of data loss if the filtering program is interrupted
This paper focuses on the design and control strategy of an embedded controller for the hydraulic quadruped robot walking robot (WLBOT)
Summary
Over the past decades, multilegged robots have gained more and more attention for their ability to traverse nonstructural environments and uneven terrains like mammals or insects. The high-level control system coordinates the behavior of the legs to regulate the velocity, attitude, and altitude of the body during locomotion in 200 Hz while the lower-level control system servos positions and forces at the joints in 1 kHz [22]. This paper gives an introduction of the quadruped hydraulic wheeled-legged robot WLBOT, including its structure, hydraulic system, and control system. The Chebyshev filtering algorithm is utilized to reduce the vibration noise of joint signals; An impedance controller in the joint space is proposed to get the better locomotion behavior and compliant effect in the walking experiments. A schematic of WLBOT onboard hydraulic system is illustrated in Figure 2 where only two joint units are displayed and the other six joint units are omitted
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