Foot Trajectory Generation of Hydraulic Quadruped Robots on Uneven Terrain

Abstract

This paper proposes trot pattern generation and online control methods for a legged robot to carry heavy-loads and move fast on the uneven terrain. The trot pattern is generated from the frequency modulated pattern generation method based on the frequency modulated oscillator in order for the legged robots to operate outdoors with the static and dynamic mobility. The efficiency and performance of the proposed are verified through the computer simulation and experiments using qRT-1/-2. In experiments, qRT which is a 2-legged and 2-wheeled robot and a front drive system vehicle with hydraulic linear actuators is used. The robot has trotted gaits at speeds up to 1.3 m/s on the even surface, walked up and down the 20 degree inclines, and walked at 0.7 m/s on the uneven surface. Also it has carried over 100 kg of the total weights including over 40 kg of the payload.

Design and Development of an Embedded Controller for a Hydraulic Walking Robot WLBOT

“…where ε is a positive number less than 1, Ω c is the passband boundary frequency. We can design a Chebyshev I Filter as Equation (11) shows, with a 70 Hz cut-off frequency. When we convert the Z transfer function into a difference equation, we can implement it in the embedded controller.…”

“…Italian Institute of Technology (IIT) constructed a series of high-performance hydraulic quadruped robots, such as HyQ [8], miniHyQ [9], HyQ2Max [10], HyQReal. Korea Institute of Industrial Technology (KITECH) proposed hydraulic quadruped robots qRT-1, qRT-2 [11], p2 [12], and JINPOONG [13]. Meanwhile, Shandong University's (SDU) quadruped robots SCalf-I [14], SCalf-II [15], and SCalf-III [16], Shanghai Jiao Tong University's (SJTU) Baby elephant [17] and Octopus [18], Harbin Institute of Technology's (HIT) MBBOT [19], National University of Defense Technology's (NUDT) quadruped robot [20] and Beijing Institute of Technology's (BIT) bionic quadruped robot [21] also continued to obtain advances in the fields of dynamic locomotion and control in recent years.…”

“…The CPU board is a Kontron MOPSPM104 board (Kontron S&T AG, Augsburg, Germany) running a real-time patched version of Linux (Linux kernel patched with real-time Xenomai), while five multifunction I/O boards are responsible for four legs and other sensors in a 1 kHz control frequency [23]. qRT-2 has a control architecture composed of the task level controller, the function level controller, the local controller, and the power controller [11]. The MIT Cheetah, whose control system is comprised of four layers: the motor drivers, the parallel UART emulators, the real-time multicore controller, and the monitoring PC, uses an i7 dual-core 1.33 GHz CPU as the real-time controller running two 4 kHz high priority loops [24].…”

Engineering research in fluid power: a review

“…The qRT-2 weighs about 60 kg and can carry over 40 kg of payload. It successfully demonstrated the trotting gaits at a speed up to 1.3 m/s on an even surface and walking at 0.7 m/s on an uneven and ramped surface (Kim et al, 2008). They also developed the 4-leg walking robot P2 in 2010 and investigated the hydraulic flow consumption during the robot's walking behaviour (Kim et al, 2010).…”

“…It aims to (a) Fig. 7 Quadruped walking robots developed by Korea Institute of Industrial Technology (a) A quadruped walking robot, qRT-2 (Reprinted from (Kim et al, 2008), Copyright 2008, with permission from IFAC); (b) A quadruped walking robot, P2 (Reprinted from (Kim et al, 2010), Copyright 2010, with permission from VDE VERLAG GMBH Berlin) (b) develop a high dynamic quadruped robot which is able to work in complex terrains with good adaptability. It can walk with an average speed of 1 m/s and a maximum speed of 1.8 m/s without a heavy load and 0.4 m/s with a load of 80 kg (Li et al, 2011).…”