Citation: Li, M.; Liu, Z.; Wang, M.;
Pang, G.; Zhang, H. Design of a
Parallel Quadruped Robot Based on a
Novel Intelligent Control System.
Appl. Sci. 2022, 12, 4358. https://
doi.org/10.3390/app12094358
Academic Editor: Augusto Ferrante
Received: 23 March 2022
Accepted: 23 April 2022
Published: 25 April 2022
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Article
Design of a Parallel Quadruped Robot Based on a Novel
Intelligent Control System
Mingying Li, Zhilei Liu , Manfu Wang, Guibing Pang and Hui Zhang *
School of Mechanical Engineering and Automation, Dalian Polytechnic University, Dalian 116034, China;
limy@dlpu.edu.cn (M.L.); liuzhilei_article@163.com (Z.L.); lzl1663063193@163.com (M.W.);
pangguibingsx@163.com (G.P.)
* Correspondence: zh1226419340@163.com
Abstract:
In order to make a robot track a desired trajectory with high precision and steady gait,
a novel intelligent controller was designed based on a new mechanical structure and optimized
foot trajectory. Kinematics models in terms of the D-H method were established to analyze the
relationship between the angle of the driving joint and the foot position. Inspired by a dog’s diagonal
trot on a flat terrain, foot trajectory planning in the swing and support phases without impact were
fulfilled based on the compound cycloid improved by the Bézier curve. Both the optimized cascade
proportional–integral–derivative (PID) control system and improved fuzzy adaptive PID control
system were applied to realize the stable operation of a quadruped robot, and their parameters were
optimized by the sparrow search algorithm. The convergence speed and accuracy of the sparrow
search algorithm were verified by comparing with the moth flame optimization algorithm and particle
swarm optimization algorithm. Finally, a co-simulation with MATLAB and ADAMS was utilized to
compare the effects of the two control systems. The results of both displacement and velocity exhibit
that the movement of a quadruped bionic robot with fuzzy adaptive PID control systems optimized
by the sparrow search algorithm possessed better accuracy and stability than cascade PID control
systems. The motion process of the quadruped robot in the co-simulation process also demonstrates
the effectiveness of the designed mechanical structure and control system.
Keywords:
quadruped bionic robot; kinematics; trajectory planning; PID controller; sparrow
search algorithm
1. Introduction
Quadruped robots have received extensive research because of their excellent stability
and carrying capacity [
1
,
2
], which are less complicated than the hexapod and eight-legged
robots [
3
,
4
]. These advantages lead to the acceptance of quadruped robots in various
working environments, both on rugged and flat ground [
5
]. The legs are the key component
determining the application performance of the quadruped robots. Therefore, many studies
have focused on the design of mechanical structure, gait planning, and motion control
algorithm to optimize the kinematic performance of the legs.
The mechanical structures of the legs of quadruped robots are mainly divided into
series and parallel forms. With respect to the study on the series structure of the robot’s
legs, Poulakakis et al. [
6
] developed telescopic column legs using springs to reduce weight
and inertia, but this led to a reduction in load capacity. Wensing et al. [
7
] constructed
articulated legs with offset-arranged joints to obtain a larger range of motion during the
movement of a robot. Li et al. [
8
] designed articulated legs using a two-link mechanism
composed of a hip flexion joint and a knee joint to simplify the mechanical structure. As
mentioned above, the robot’s legs of the series structure are simple and have a large working
space, but also have the disadvantages of low load capacity, complicated control systems,
and high cost. These shortcomings are usually addressed using parallel structural legs.
Appl. Sci. 2022, 12, 4358. https://doi.org/10.3390/app12094358 https://www.mdpi.com/journal/applsci
