Obstacle-surmounting Capability Research Articles

Reconfigurable design of a passive locomotion closed-chain multi-legged platform for terrain adaptability

In order to enhance the adaptability of closed-chain multi-legged platform to uneven terrain, a reconfigurable passive locomotion closed-chain platform (RPCP) is proposed. On the basis of our previous research which focused on the locomotion on structured ground, we adopt reconfigurable design for trajectory flexibility. First, based on kinematics analysis, a reconfigurable design of the leg mechanism is proposed and adjustable trajectory parameters are analysed. Next, for the whole platform, reconfigurable assignments and strategies are analysed to satisfy different obstacle-surmounting requirements. Finally, a series of dynamic simulations and experiments are performed to testify the RPCP's walking performance and its passive obstacle-surmounting capability. It is shown that the RPCP can walk and accelerate on relatively slippery or soft ground, and can climb obstacles such as slopes and vertical walls by vector thrust. The research of RPCP provides a vector thrust-propelled method of reconfigurable closed-chain legged platform to improve the adaptability to terrain.

Design and Analysis of a Multi-Legged Robot with Pitch Adjustive Units

The paper proposes a novel multi-legged robot with pitch adjustive units aiming at obstacle surmounting. With only 6 degrees of freedom, the robot with 16 mechanical legs walks steadily and surmounts the obstacles on the complex terrain. The leg unit with adjustive pitch provides a large workspace and empowers the legs to climb up obstacles in large sizes, which enhances the obstacle surmounting capability. The pitch adjustment in leg unit requires as few independent adjusting actuators as possible. Based on the kinematic analysis of the mechanical leg, the biped and quadruped leg units with adjustive pitch are analyzed and compared. The configuration of the robot is designed to obtain a compact structure and pragmatic performance. The uncertainty of the obstacle size and position in the surmounting process is taken into consideration and the parameters of the adjustments and the feasible strategies for obstacle surmounting are presented. Then the 3D virtual model and the robot prototype are built and the multi-body dynamic simulations and prototype experiments are carried out. The results from the simulations and the experiments show that the robot possesses good obstacle surmounting capabilities.

Design and terrainability analysis of a novel mobile robot with variable-diameter wheels

Mobile robots are usually demanded to enter into unstructured terrain. Thus, terrainability of a robot is specially important in cluttered environments. A novel mobile robot with variable-diameter wheels is designed here. This robot can adjust its attitude by variable wheel diameters to improve its terrainability. For terrainability, stability and obstacle-surmounting capability of the robot are studied. Furthermore, variable wheel diameters’ effects on these performances were researched. For lateral and longitudinal stabilities, parametric relationships between the maximum slope that the robot can climb and stability requirements were obtained. To avoid stability failures, appropriate failure criterions were proposed. Stability of the robot can be enhanced by changing wheel diameters. The obstacle-surmounting performances of front and rear wheels were analyzed by building two quasi-static models. The results showed that increased wheel diameters enhanced the obstacle-surmounting height. The analytical calculations and the simulations were compared. The simulations verified the reliability of the theoretical calculations. Based on tip-over failure criterions, appropriate strategies can be used to enhance the stability. These analysis presented also can provide theoretical basis for performance optimization design of the robot.

Design and Analysis of a Sixteen-Legged Vehicle With Reconfigurable Close-Chain Leg Mechanisms

In order to exert the advantages of simplified control and integral rigidity, a novel 16-legged walking vehicle is proposed as a carrying platform based on closed-chain mechanisms. Considering the demand for mobility of one degree-of-freedom leg mechanism, we adopt the reconfigurable approach for trajectory flexibility. Serving as a walking module, the whole close-chain leg mechanism is designed to construct the walking vehicle. On the basis of kinematic analysis and sensitivity analysis, the reconfigurable leg with “gluteus maximus” is presented for increasing the obstacle-surmounting ability. In terms of the whole vehicle, the reconfiguration assignments and strategies are analyzed to satisfy the different climbing requirements. The obstacle-climbing capabilities of the legged units are evaluated through the probability analysis. In slope-climbing process, the supporting and the propelling regions for reconfiguration are discussed and obtained with two decision conditions. A series of dynamic simulations and experiments are performed to testify the walking stability, the walking speed, the steering performance, the terrain adaptability, and the obstacle-surmounting capability.

Design and analysis of a novel walking vehicle based on leg mechanism with variable topologies

In order to improve the adaptability of one-degree-of-freedom leg mechanism to unknown terrains while maintaining its control simplicity, energy efficiency and integral rigidity, a novel close-chain mechanism with variable topological structures is proposed to act as a single leg to generate different gaits. The design process of the closed kinematic chain is completed by integrating two types of mechanical joints. Besides, the kinematics of the single leg under two modes is analyzed using vector loop method, and the particular structure of the leg mechanism is designed with optimized parameters. The topological states are represented with graphs and a matrix. Moreover, the whole close-chain legged unit and the walking vehicle are developed and constructed. In particular, to evaluate the crossing ability, this paper proposes the obstacle-surmounting probability. A series of dynamic walking simulations is conducted and analyzed to support the obstacle-surmounting capability and mobility comparison. Legged units are fabricated to verify the theoretical analysis, and walking experiments with a multi-legged vehicle are performed to testify the prototype performance.

Designing and Analyzing For a Bar Linkage Obstacle-Surmounting Robot with the Same Phase in all the Wheels

In order to improve the obstacle-surmounting capability of robots in complex, we propose a new bar linkage type obstacle-surmounting robot with the same phase in all the wheels(BOSWbot). The robot relies on its special mechanism which all the wheels in the same phase to overcome the “singular point” problem of the single-bar over-obstacle robot. The torque of the different motors is integrated to improve the running velocity. In addition, we research a new type of wheel which is made of different materials. The robot uses the different friction in wheel surface to solve the turning problem. Finally, the way to travel of the bar linkage obstacle-surmounting robot makes it switch to the obstacle mode automatically. Then the robots complete the process of climbing obstacle.

Mechanical Analysis of the Jumping Motion of a Spherical Robot

The obstacle surmounting capability of traditional spherical mobile robot is limited, especially when the spherical mobile robot comes across vertical barrier. In this paper we design a new kind of spherical mobile robot with two-mass-one-spring mechanism based on tradition spherical mobile robot. This spherical robot could not only move agility and move with the zero turning radius like traditional spherical mobile robot but also jump in three-dimensional space. In this paper we build the mathematical model of robot jumping with friction. Numeric simulations are carried out for the model using Matlab and ADAMS, we get the similar curve. These simulation results verify the validity of the mechanics model. At last we design an experimental facility, verify the model of robot jumping by experiment. Our work will be the base of model machine designing.

Obstacle-surmounting Mechanism and Capability of Four-track Robot with Two Swing Arms

For performing the best obstacle-surmounting capability of four-track robot with two swing arms, obstaclesurmounting mechanism of the four-track robot with two swing arms and its capabilities of surmounting obstacles, including step and slope-climbing, and channel-crossing, are analyzed from the viewpoint of kinematics based on the obstaclesurmounting mechanism of the fixed two-track robot. Its motion mechanism and maximal obstacle-surmounting capability of step-climbing forward and backward are mainly analyzed. Taking CUMT-II coal mine exploring robot prototype as an example, three dimensional relationship diagrams of the step height, the elevation angle and arms’ swing angle are drawn and the relation curves of slope gradients and the swing arms’ swing angles are drawn. The theoretical value of maximal obstacle-surmounting capabilities of the prototype are obtained and compared with the test results. And the best obstaclesurmounting performance and the corresponding centroid and swing arm positions are deduced. This paper would provide theoretical basis for centroid position control in obstacle-surmounting process.