Adaptive Variable Parameter Impedance Control for Apple Harvesting Robot Compliant Picking

Ji Wei,Xu Bo,Chen Guangyu,Ding Yi,Zhao Dean

doi:10.1155/2020/4812657

Abstract

In order to reduce the damage of apple harvesting robot to fruits and achieve compliant picking, an adaptive variable parameter impedance control method for apple harvesting robot compliant picking is proposed in this paper. Firstly, the Burgers viscoelastic model is used to characterize the rheological properties of apples and study the variation of mechanical properties of apple grasping at different speeds. Then, a force-based impedance control system is designed. On this basis, aiming at the influence of impedance controller parameters on contact force, three impedance parameters self-tuning functions are constructed to complete the design of an improved force-based impedance control system based on the hyperbolic secant function. The simulation and experimental results show that the proposed control makes the desired force smoother, and its overshoot is about 2.3%. The response speed is faster, and the adjustment time of contact force is shorter of about 0.48 s. The contact force overshoot is about 2%, which is 37.5% less than that of the traditional force-based impedance control. This research improves the control performance for apple harvesting robot compliant picking.

Highlights

With the development of modern agriculture, harvesting robot is becoming an important area of robot application.e picking operation of harvesting robot is the key link to realize the automation and mechanization of fresh fruit and vegetable harvesting [1]
In order to solve the problem of rapid compliant picking, many scholars have conducted a lot of research studies, and many studies have applied impedance control to it
To realize the flexible adjustment of force and position of the manipulator under high-speed clamping and achieve good tracking effect, a robust impedance control method was proposed [3]. e grasping constraint relationship between the end-effector of robot and the fruit was equivalent to a second-order impedance-admittance model. e deviation between the desired grasping force and the contact force of fruit was used as the input of the impedance controller, and the reference trajectory was corrected to form an impedance tracking control for the grasping force of the end-effector which was suitable for double-fingered grasping [4]

Summary

Introduction

With the development of modern agriculture, harvesting robot is becoming an important area of robot application.e picking operation of harvesting robot is the key link to realize the automation and mechanization of fresh fruit and vegetable harvesting [1]. To realize the flexible adjustment of force and position of the manipulator under high-speed clamping and achieve good tracking effect, a robust impedance control method was proposed [3]. E grasping constraint relationship between the end-effector of robot and the fruit was equivalent to a second-order impedance-admittance model. E precise position tracking of the manipulator in free space was realized, and the grasping force can be tracked accurately through a smooth transition to the constraint space [5]. In order to study the effect of fruit-finger interaction parameters on the probability of thumb-index finger stability grip, a logistic regression model was used to reasonably predict the probability of two-finger stability grip and to analyze the grasp of two-finger force of picking robot [7]. Semini et al studied the problem of active impedance to improve the stability and usefulness of legged robots. ese research studies demonstrated the advantages and the potential of active impedance and torque-controlled robots within a series of new experiments

Objectives

Methods

Results

Conclusion