Kun Wang

Analysis of the kinematics of module climbing caterpillar robots

Based on the vermicular motion of the pine caterpillar and inchworm, this paper presents two novel module climbing caterpillar kinematics models. The analysis of the valid gaits and climbing safety of them indicates the differences of two models. The pine caterpillar model with all active joints has the disadvantage of introducing the redundant actuating to its locomotion but higher security than the inchworm model because of its more valid gaits. Two prototypes following the above two models are respectively constructed from some newly developed real adhesion and actuation modules to testify the climbing abilities of two caterpillar-like robots. The experiments show the sideslip of the suckers on the pine caterpillar robot induced by the redundant actuating and the locomotion ability of the inchworm robot on vertical wall. Besides that, an unsymmetrical gait is adopted by the inchworm robot to improve its adhesion reliability on the wall. At last, a new kinematics model of the pine caterpillar robot based on passive joints is proposed to solve the redundant actuating problem.

Principle and Application of Vibrating Suction Method

In this paper a new suction-to-wall method is presented, which is called vibrating suction method (VSM). With this method, the vacuum in the suction cup is established through high-frequency vibration of the cup with respect to the wall surface. First, the principle of the VSM is studied. Based on some assumptions, the mathematic model of a vibrating suction cup is built. Then numerical simulation of the model shows the relationship between the pressure in the cup and vibration frequency and amplitude. In the end, a prototype of suction module is designed based on the principles of the VSM, and wall suction experiments prove the effectiveness of this module. This new-style suction module is supposed to be used in miniature wall climbing robot.

The Mechanical Properties of a Wall-Climbing Caterpillar Robot: Analysis and Experiment

This paper builds the kinematic model of a wall-climbing caterpillar robot to reveal the validity and the benefits of the closed-chain kinematics of the four-linkage mechanism to a crawling gait. The caterpillar robot can climb on a vertical wall by coordinating the rotations of one active joint and three passive joints. The mechanical property of the closed-chain kinematics of the four-linkage model is analysed. Furthermore, the relation between the driving joint torque and joint angle in the wall-climbing process is deduced based on the coplanar arbitrary force system. Afterwards, the joint control method is discussed in order to coordinate the rotation of the four joints so as to realize a reasonable wall climbing gait. To testify to the availability of the closed-chain four-linkage model, a wall-climbing caterpillar robot is developed with three different adhesion modules based on the vibrating suction method. A successful wall-climbing test confirms both the practicality of the four-linkage model and the validity of the adhesion modules based on the vibrating suction method. The results also show the reasonableness of the driving joint selection rule for ensuring a safe and reliable wall-climbing procedure.

Analysis of Gait and Mechanical Property of Wall-climbing Caterpillar Robot

In order to demonstrate the validity and the benefit of the closed-chain kinematics of four-link motional method for the gait of wall-climbing caterpillar robot, the mathematical model and the relation of kinematical parameters were built. The caterpillar robot can climb on the wall by coordinated rotation of one active joint and three passive joints. The mechanical property of the closed-chain kinematics of four-link method is analyzed. And the relation of the driving joint torque and joint angle in wall-climbing process is deduced based on coplanar arbitrary force system. The coordinated control of multiple joints and the basis for selecting driving joints were discussed for developing the wall-climbing caterpillar robot. To testify the availability of the closed-chain kinematics of four-link method, a prototype of wall-climbing caterpillar robot with three kinds of adhesion modules based on vibrating suction method is designed. A successful wall-climbing test confirms both the principles of the closed-chain kinematics of four-link method and the validity of the adhesion modules based on vibrating suction method. The results show that the basis for selecting driving joints was reasonable and that the adhesion module based on vibrating suction method can produce powerful adsorption force with small weight and volume to ensure the safety and reliability of wall-climbing.

Internal force compensating method for wall-climbing caterpillar robot

The redundant driving problem is an inherent phenomenon existing in a modular caterpillar robot. To limit the internal forces arising from the redundant driving, this paper proposes a joint torque control method, which is based on an assumption that there is only one active joint in the four-link mechanism driving the climbing gait. Except the active joint, the other three joints are all considered as passive joints, whose torques tend to be zero, although they are driven by motors in reality. According to the analyses of static forces in the closed chain state, the ideal torque of named active joint is calculated, and will be followed by the joint in real climbing locomotion. The experiments reveal the reasonability and feasibility of the proposed joint control method, as well as the limitations of current prototype and control algorithm.

Analysis of two vibrating suction methods

In this paper, a novel vibrating method based on the principle of vibrating suction method is presented, which is called pulse vibrating method. To discuss this method in depth and evaluate its performance, simplified mathematical model based on some assumptions for both the previous sin vibrating method and the pulse vibrating method are built, and a new experimental platform is developed as well to verify the validity of the mathematical models. The experiments indicate that the experiments meet the mathematical model with only small deviation caused by some unknown factors. The experimental results also show that the pulse vibrating method is much better than the sin vibrating method for higher negative air pressure and less power consumption. At the end of this paper, conclusion is given and future work is proposed to further analyze the principle of the vibrating suction method.

Development of modular wall-climbing robot inspired by natural caterpillar

This paper investigates the locomotion mechanism and crawling gait of our modular wall-climbing caterpillar robot. The concept of a modular wall-climbing caterpillar robot is inspired by the kinematics of the natural caterpillar. Two kinds of modules, which are attachment module and joint module, were developed. Due to the fixed constraints between the suction cups and wall, the gait of the caterpillar robot engages a changing kinematic chain which is from an open chain to a closed chain, and then to an open chain orderly. The discussion of this paper is focused on the crawling gait adopted by our prototype and on locomotion realization. In the closed chain state, a four links kinematics model is adopted to fulfill the fixed constraints produced by the attached suckers. In the end, a successful on-site tests confirm the above principles and the validity of the climbing gait.

Analysis of gait control of wall-climbing caterpillar robot

In order to verify the benefit of four links kinematical method, the mathematical model of four links kinematics is established. The kinematical parameters of passive joints can be calculated according to the rotation of active joint. Then the wall-climbing robot can climb the vertical wall through the coordinated rotation of active joint and passive joints. To testify the feasibility of the four links kinematical method, a wall-climbing caterpillar robot based on vibrating suction method is developed. An experiment of wall-climbing confirms the kinematical method mentioned above. The result shows that the four links kinematical method is simple and reliable although some errors exist. At last, the conclusions and future works are present.

Gait control of modular climbing caterpillar robot

The concept of a modular climbing caterpillar robot is inspired by the kinematics of the real caterpillar. Due to the fixed constraints between the suckers and wall, the gait of the caterpillar robot engages a changing kinematic chain which is from an open chain to a closed chain, and then to an open chain orderly. This paper investigates the joint control methods of the gait in detail. During the open chain periods, an Unsymmetrical Phase Method (UPM) is applied to ensure the reliable attachment of the passive suckers to the wall. But in the closed chain state, a four links kinematics model is adopted to fulfill the fixed constraints produced by the attached suckers. By combining the two methods together, we acquire complete joint control trajectories for a modular caterpillar robot with seven joints. At the end of this paper, on-site tests confirm the above principles and the validity of the climbing gait.

Development and Experiment of Wall-Climbing Caterpillar Robot

In order to demonstrate the validity and the benefit of the closed-chain kinematics of four-link motional method for the gait of wall-climbing caterpillar robot, the mathematical model and the relation of kinematical parameters were built. The caterpillar robot can climb on vertical wall by coordinated rotation of one active joint and three passive joints. To testify the availability of the closed-chain kinematics of four-link method, a prototype of wall-climbing caterpillar robot with three kinds of adhesion modules was designed. A successful wall-climbing experiment confirms the principles of the closed-chain kinematics. The results show that the basis for selecting driving joints was reasonable and that the adhesion module can produce powerful adsorption force with small weight and volume to ensure the safety and reliability of wall-climbing.