Optimal Design of a Five-Bar Leg Mechanism for a Quadruped Robot
In this paper, a five-bar leg mechanism is designed and optimized in the context of the quadruped robot. The kinematics and statics of the five-bar leg mechanism is analyzed. The goal of this paper is to design a leg with a load capacity of 30 kg and a wa
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Abstract. In this paper, a five-bar leg mechanism is designed and optimized in the context of the quadruped robot. The kinematics and statics of the five-bar leg mechanism is analyzed. The goal of this paper is to design a leg with a load capacity of 30 kg and a walking speed of 0.5 m/s. Under the given conditions, it’s necessary to obtain optimal link length parameters so that the maximum torque and angular velocity required for the motors are minimum. And the genetic algorithm is used to obtain the optimal solutions of the overall performances. In addition, comparative study verifies the correctness and effectiveness of the optimization.
Keywords: Quadruped robots
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· Five-bar mechanism · Optimal design
Introduction
For years, quadruped robots have been a research hotspot in the field of mobile robots because they have brilliant mobile performance on unstructured terrains. Quantities of researchers pay attention to the development of quadruped robots. And quite a few quadruped robots, like BigDog [1], ANYmal [2], Cheetah [3], HyQ [4], StarlETH [5], use the animal-like serial mechanism to construct legs. However, quadruped robots with serial legs mechanism tend to have poor load capacity, so that their applications are very limited. This paper propose a quadruped robot leg based on five-bar mechanism. Compared with serial leg mechanism, the parallel five-bar leg mechanism can carry much more weight since there are two motors mounted on the torso to support the body in company. Besides, leg’s inertia gets lower because no actuators or sensors fixed on the leg. The contribution of this paper is the optimization methods for the quadruped robots. Although a great many researchers have put forward lots of mechanism optimization methods [6,7], few of them are in the context of quadruped robots. This paper propose an original optimal design method to improve the performance of quadruped robots. This paper aims to reduce the peak torque and peak angular velocity required for the motors under the same circumstances, which is related to the design of c The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 Y. Jia et al. (Eds.): CISC 2020, LNEE 706, pp. 171–179, 2021. https://doi.org/10.1007/978-981-15-8458-9_19
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legs. And a multi-objective optimal model is built to achieve the goal of improving the performance of it. The rest of the paper is organized as follows. In Sect. 2, the kinematics and statics of the leg is analysed based on the quadruped robot model presented. In Sect. 3, a multi-objective optimal model is constructed to obtain the link length to have better performances. Section 4 shows the optimal results and verifies the correctness and effectiveness. Finally, the conclusions are drawn in Sect. 5.
2 2.1
Kinematics and Statics of the Five-Bar Mechanism Inverse Kinematics
The quadruped robot whose leg is composed of five-bar mechanism is presented in Fig. 1(a). It’s a planar five-bar structure with two degree of freedoms. The leg is dr
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