Design of a micro pole-climbing robot

Abstract

Pole-climbing robots are increasingly needed to carry out high-risk tasks for human beings. A micro pole-climbing robot is designed in this article. A strategy of climbing pole is proposed, which has high precision in each stride. To enable the robot to sample the angle relative to the ground in real time, micro electro mechanical systems (MEMS) three-axis accelerometers are equipped on micro pole-climbing robot. Accelerometer measurements provide an absolute reference for the pitch-and-roll components of the estimated orientation, which are used as feedback input signal of proportionalintegral-derivative algorithm. A supporting structure is installed at the joint of each gripper to assist the robot to clamp a pole. The support structure improves the load capacity of the robot. The maximum load of micro pole-climbing robot is 3.5 times its own weight. The climbing pole strategy includes the following sections: a Denavit-Hartenberg model is established and the inverse kinematic solution is analyzed; the flip locomotion is analyzed; and the parameters of K P , K I , and K D in the proportional-integral-derivative control method are obtained according to the Ziegler-Nichols controller. The performance of pole climbing based on micro pole-climbing robot prototype was tested. By using this strategy of climbing pole, the self-continuous climbing with controllable stride is realized, and the angular velocity fluctuation of the five-bar mechanism driven by steering gear is reduced. The average time of a single step is 27 s, the maximum relative error of step distance is 4.6%, and the average relative error is 2.8%. These results confirm that the structure scheme and the strategy of climbing pole are feasible.

The obstacle-surmounting analysis of a pole-climbing robot

“…The flipping-over gait of PCRobot is decomposed into two stages: flip and stride, which are described in Qiaoling et al 18…”

“…The kinematics analysis and inverse kinematics solutions of PCRobot are described in Qiaoling et al 18…”

“…In the upright posture, the order of the four joints in the counterclockwise is j 3 , j 2 , j 1 , and j 0 , as shown in Figure 4 “upright posture.” The D-H coordinate system of PCRobot has been derived elsewhere. 18 When the robot turns over, its posture changes to the inverted posture. At this time, the order of the four joints is changed to j 0 , j 1 , j 2 , and j 3 , as shown in Figure 4 “inverted posture.” The D-H coordinate system of PCRobot has been adjusted accordingly.…”

“…For upward vertical climbing, the climbing execution is divided into four steps: loosening the lower gripper, curling up, striding forward, and clamping the upper gripper. Take the reversal process from the inverted posture to the upright posture as an example, the climbing control process is as follows: the steering gear s 0 rotates to loosen the lower gripper g 1 ; the steering gears s 1 , s 2 , s 3 , and s 4 rotate to curl up at a fixed angle; the steering gears s 1 , s 2 , s 3 , and s 4 rotate to stride forward according to the calculated angle (see Qiaoling et al 18 for details), and the steering gear s 0 rotates to clamping the upper gripper g 1 .…”

“…As shown in Figure 6(a), each linkage is described by only one segment, and the two ends of the segment are the joints. The coordinates of the joints can be directly solved by using the D-H model of the robot linkage structure mentioned in Qiaoling et al 18 Because of the thickness of the robot structure, the dynamic description of R ′ becomes complex. As shown in Figure 10, the thickness area edge of each linkage needs to be described by multiple segments, and the end points of the segments deviate from the joints, which leads to a complex shape of R ′ .…”