Wheel-legged Robot Research Articles

Mechanism Synthesis of a Transformable Wheel-Legged Robot

Based on synthesizing the robot’s chassis mechanism,a transformable chassis is presented to adapt to the conflictive requirements of complex fields. A transformable wheel-legged robot has been designed with the applied chassis. As a variable topology mechanism, the robot has many changeable configurations. Finally the structure implementation of the robot was discussed.

Kinematic Research of the Multi-Motion Pattern Bionic Mechanism

In this paper, a new multi-motion pattern bionic robot was proposed by us. Though we analyzed the robot as a hybrid series-parallel mechanism, the robot is a wheeled-legged robot, and a new methods for constructing the kinematic model of the special four-bar mechanism of the robot very quickly and efficiently was introduced. Then, the kinematic model of the parallel mechanism of the multi-motion mode bionic robot was constructed when the robot was in the stance phase.

Real-Time Motion Generation and Control Systems for High Wheel-Legged Robot Mobility

A wheel-legged mobile robot (WLMR) has both leg and wheel structures. WLMRs have adaptability advantages because they can change locomotion methods depending on the terrain. However, the location of a WLMR's center of gravity (CoG) is very high; thus, almost all existing WLMRs move statically. In this paper, whole body motion generation and various control systems are studied to facilitate higher WLMR mobility. To this end, a zero moment point (ZMP) is introduced as a stability index. In addition, WLMRs are modeled as single point mass linear inverted pendulums. Subsequently, online CoG pattern generation methods are proposed; one is a preview control approach, and a second is an approach that realizes the desired ZMP pattern using a zero-phase low-pass filter. It is then possible to generate the desired CoG patterns more easily and faster than with a preview control approach. The CoG patterns based on the single point model are constructed via the resolved-momentum-control approach. Finally, the effectiveness of the whole body motion pattern generated by the proposed methods is validated by simulations and experiments.

A Design of Leg-Wheeled Robot with Reduced DOF and Passive Wheels

A Design of Leg-Wheeled Robot with Reduced DOF and Passive Wheels

Mantis: hybrid leg-wheel ground mobile robot

Purpose – The aim of the research is the development of a small-scale ground mobile robot for surveillance and inspection; the main design goals are mobility in indoor environments with step climbing ability, pivoting around a vertical axis and without oscillations for stable vision, mobility in unstructured environments, low mechanical and control complexity. Design/methodology/approach – The proposed hybrid leg-wheel robot is characterized by a main body equipped with two actuated wheels and two praying Mantis rotating legs; a rear frame with two idle wheels is connected to the main body by a vertical revolute joint for steering; a second revolute joint allows the rear axle to roll. The geometrical synthesis of the robot has been performed using a nondimensional approach for generality's sake. Findings – The experimental campaign on the first prototype confirms the fulfilment of the design objectives; the robot can efficiently walk in unstructured environments realizing a mixed wheeled-legged locomotion. Practical implications – Thanks to the operative flexibility of Mantis in indoor and outdoor environments, the range of potential applications is wide: surveillance, inspection, monitoring of dangerous locations, intervention in case of terroristic attacks, military tasks. Originality/value – Different from other robots of similar size, Mantis combines high speed and energetic efficiency, stable vision, capability of climbing over high steps, obstacles and unevenness.

Feedforward Compensation Methods for Zero Moment Point Error from Gyrating Locomotion of Wheel-Legged Mobile Robot based on Previewing Centrifugal Force

Feedforward Compensation Methods for Zero Moment Point Error from Gyrating Locomotion of Wheel-Legged Mobile Robot based on Previewing Centrifugal Force

Study on Characteristics of Passive Wheel Typed Robot

This paper put forward a new type of leg-wheeled hybrid mobile robot installed passive wheels at the ends of the legs, we call this typed robot as Ice-skater robot, An analysis and improvement upon the original structure of skating robot is proposed, The paper gives the model of the robot kinematics and a simulation was carried out upon the moving characteristics of the skating robot while it was sliding.

Study on Kinematics of a Ice-Skater Robot of Passive Wheel Type and its Structure Characteristics

This paper put forward the idea of ice skater robot of passive wheeled type integrating the features of wheeled mobile robots and legged mobile robots. The motion principle of a kind of leg-wheeled robot was analyzed. On the basis of introduction of kinematics analysis, the paper gives the model of the robot kinematics, Meanwhile, the paper analyzes the motion condition of the robot.

Dynamic Analysis of the Wheel-Legged Mobile Robot

The design of the wheel-legged mobile robot is mainly used for the early toxic gas leakage warning and disaster relief in the field of wild environment. The robot needs to cross some obstacles such as ditch and step when carrying out a task. The paper analyzes the strategies of robot passing the all kinds of obstacles. Considering the influence of disturbance by uneven road surface, the dynamic model of robot crossing the step and groove on the uneven road surface is built based on the robots structural features. While the control model of front wheel-leg is also presented based on the robot dynamic model. The results of simulation expriments demonstrate the correctness of the built dynamic model and laid the foundation for the design of the robot control system.

Research on Kinematic of the Wheel-Legged Robot Based on Uneven Road Surface

A new type of wheel-legged mobile robot is presented in the paper, which is mainly used for early toxic gas leakage warning and disaster relief in the field of wild environment. The paper first presents the structure feature of the new wheel-legged mobile robot. According to the structure of the robot, the kinematics model about robot moving on the smoothing-riding surface is built. On this basis, considering the effects of the disturbance by uneven road surface the paper carries out the robots kinematics analysis. To simulate the result of robot moving on the real road surface, the paper researches on the robots kenimatics by inputing some typical ground driving to the robot. The result of the simulation experiment shows that the robot pose error is more increasing. So the influence of ground disturbance to robot should be took into account in designing the control symstem, which can decrease the pose error and make robot move more accurately.

Stability Control and Simulation of Wheel-Legged Mobile Robot in Mechanical Engineering

The wheel-legged mobile robot in a complex three-dimensional environment has strong through capacity .Study is very critical for the stability of the control of their body systems. In this paper , based on analysis of the structure of wheel-legged mobile robot designed, the stability is evaluated by the use of (Effective Mass Center) EMC , and the stability domain is established accordingly. A fuzzy adaptive PID control method is created , and verified by ADAMS and MATLAB co-simulation . Simulation results show that the robot in different terrestrial environment, can maintain good stability.

Dynamics and wheel's slip ratio of a wheel-legged robot in wheeled motion considering the change of height

The existing research on dynamics and slip ratio of wheeled mobile robot (WMR) are derived without considering the effect of height, and the existing models can not be used to analyze the dynamics performance of the robot with variable height while moving such as NOROS-II. The existing method of dynamics modeling is improved by adding the constraint equation between perpendicular displacement of body and horizontal displacement of wheel into the constraint conditions. The dynamic model of NOROS-II in wheel motion is built by the Lagrange method under nonholonomic constraints. The inverse dynamics is calculated in three different paths based on this model, and the results demonstrate that torques of hip pitching joints are inversely proportional to the height of robot. The relative error of calculated torques is less than 2% compared with that of ADAMS simulation, by which the validity of dynamic model is verified. Moreover, the relative horizontal motion between fore/hind wheels and body is produced when the height is changed, and thus the accurate slip ratio can not be obtained by the traditional equation. The improved slip ratio equations with the parameter of the vertical velocity of body are introduced for fore wheels and hind wheels respectively. Numerical simulations of slip ratios are conducted to reveal the effect of varied height on slip ratios of different wheels. The result shows that the slip ratios of fore/hind wheels become larger/smaller respectively as the height increases, and as the height is reduced, the reverse applies. The proposed research of dynamic model and slip ratio based on the robot height provides the effective method to analyze the dynamics of WMRs with varying height.

Analysis for Obstacle Negotiation Capability of Wheel-Legged Robot

Obstacle negotiation capability is important to a mobile robot. A wheel-legged robot with symmetrical structure was presented It has four independent wheel-legged articulations which can generate a series of conFigureurations to improve its trafficability. The obstacle negotiation capability of the robot was studied. Its step-climbing process was described, and the geometrical and dynamic model for the process was built. Based on comprehensively considering geometrical and dynamic constraints, the method to work out the maximal step height that the robot can get across was brought forward. Then the method to work out the maximal slope angle was also provided. Finally the experiment to verify the above methods was done. The research mentioned above would provide a theoretical foundation to improve the robot’s adaptability in complicated environments.

Running Model for a Compliant Wheel-Leg Hybrid Mobile Robot by Using a Mass-Spring Model

This research presents a running model for a compliant wheel-leg hybrid mobile robot. A wheel-leg consists of three legs arranged by 120 degrees to each other and passive compliant joints. For simplicity, each leg is treated as a linear spring such that a traditional mass-spring model can be applied to model running of the wheel-leg hybrid robot. In order to achieve stable running, we propose a simple controller that can converge a robot leg to a desired angle of attack asymptotically during the swing phase. Hybrid wheel-leg running is then simulated and results are discussed.

고관절 구동 방식을 갖는 바퀴-다리형 로봇과 지면 간 접촉점에서의 마찰계수 추정

This paper presents the estimation of the frictional coefficient of the wheel-legged robot with hip joint actuation producing maximum tractive force. Slip behavior for wheel-legged robot is analytically explored and physically understood by identification of the non-slip condition and derivation of the torque limits satisfying it. Utilizing results of the analysis of slip behavior, the frictional coefficients of the wheel-legged robot during stance phase are numerically estimated and finally this paper suggests the pseudo-algorithm which can not only estimate the frictional coefficients of the wheel-legged robot, but also produce the candidate of the touch down angle for the next stance.

Development of a Hybrid Wheel-Legged Mobile Robot WR-3 Designed for the Behavior Analysis of Rats

This paper presents the design and development of a bio-inspired mobile robot called WR-3 (Waseda Rat no. 3). The purpose of the robot is to work as an experimental tool to study social interaction between rats and robots. According to the results of the analysis of the motion of rats, their behavior can be divided into two phases: movement and interaction. Therefore, a novel hybrid mechanism that uses wheels during the movement phase and legs while interacting has been designed to actuate WR-3. Consequently, the robot can move at a high speed using its wheels, and reproduce the rat's interaction behavior using its legs and other parts. Based on body structure of a mature rat, WR-3 has been designed with similar dimensions and shape as a mature rat, and the quality of the shape imitation has been verified by the experiments of a rat's interestingness to the robot and stuffed rat. Evaluation experiments show that WR-3 is capable of reproducing a rat's actions such as chasing, rearing, grooming, mounting, etc., similar to a real rat. Furthermore, preliminary social interaction tests with living rats reveal that WR-3 is to some extent able to evoke natural reactions form a real rat and is therefore able to perform a certain level of realistic interaction.

Dynamic Modeling for Obstacle Negotiation of Wheel-Legged Robot and Analysis on Its Influential Factors

The dynamic analysis of a wheel-legged robot with multiple drive modes is studied.Firstly,the vertical obstacle negotiation process is described,then the dynamic model for the process is built.The torque distribution between all motors,the influential factors of movement states and gravity allocation are included in the model.By means of the investigation of the whole process,the utmost states of two kinds of motors' torque in the driving system are ascertained.The influences of different factors on the maximal output torques are analyzed and the method to work out the maximal height that the robot can rove through is brought forward finally.The result will provide a theoretical foundation to improve the robot's adaptability in complicated environments.

Idea of wheel-legged robot and its control system design

The wheel-legged robot is a vehicle with many degrees of freedom. Thanks to its peculiar design, depending on the need, the vehicle will use one of its ways of moving: travelling on wheels or walking (in special situations), which enhances its locomotive properties. The paper presents the robot’s kinematic wheel suspension system, general operation strategy and control system. The application responsible for robot control and data visualization is described. Finally, selected tests of the algorithms, carried out on the robot prototype, are presented.

Dynamic Simulation-Based Action Planner for a Reconfigurable Hybrid Leg–Wheel Planetary Exploration Rover

In this paper, an action planning algorithm is presented for a reconfigurable hybrid leg–wheel mobile robot. Hybrid leg–wheel robots have recently receiving growing interest from the space community to explore planets, as they offer a solution to improve speed and mobility on uneven terrain. One critical issue connected with them is the study of an appropriate strategy to define when to use one over the other locomotion mode, depending on the soil properties and topology. Although this step is crucial to reach the full hybrid mechanism's potential, little attention has been devoted to this topic. Given an elevation map of the environment, we developed an action planner that selects the appropriate locomotion mode along an optimal path toward a point of scientific interest. This tool is helpful for the space mission team to decide the next move of the robot during the exploration. First, a candidate path is generated based on topology and specifications' criteria functions. Then, switching actions are defined along this path based on the robot's performance in each motion mode. Finally, the path is rated based on the energy profile evaluated using a dynamic simulator. The proposed approach is applied to a concept prototype of a reconfigurable hybrid wheel–leg robot for planetary exploration through extensive simulations and real experiments.

Motion kinematics analysis of wheeled–legged rover over 3D surface with posture adaptation

This paper proposes a general formulation of the kinetostatic model of articulated wheeled rovers that move on rough terrains. Differential kinematic model is used to control the generalized trajectory of the robot, composed of position and posture parameters. These posture parameters have been optimized in order to provide high stability and traction performance, during motion on irregular ground surface. Numerical simulation and experimental results, carried out on a hybrid wheeled-legged robot, show the validity of the approach presented in this paper.