Development of a stair-climbing mobile robot with legs and wheels

This paper deals with the development of a stair-climbing mobile robot with legs and wheels. The main technical issues in developing this type of robot are the stability and speed of the robot while climbing stairs. The robot has two wheels in the front of the body to support its weight when it moves on flat terrain, and it also has arms between the wheels to hook onto the tread of stairs. There are two pairs of legs in the rear of the body. Using not only the rorational torque of the arms and the wheels, but also the force of the legs, the robot goes up and down stairs. It measures the size of stairs when going up and down the first step, and therefore the measurement process does not cause this robot to lose any time. The computer which controls the motion of the robot needs no complicated calculations as other legged robots do. The mechanism of this robot and the control algorithm are described in this paper. This robot will be developed as a wheelchair with a stair climbing mechanism for disabled and elderly people in the near future. This work was presented, in part, at the International Symposium on Artificial Life and Robotics, Oita, Japan, February 18–20, 1996     

Gait optimization of step climbing for a hexapod robot

RHex-style hexapod robot is a type of legged robot which can perform multiple moving gaits according to different applications, due to its simple structure and strong mobility. However, traversing high obstacles has always been a big challenge for legged robots. In this paper, gait optimization of a hexapod robot is proposed for climbing steps at different heights, which even enables the robot to climb the step 3.9 times of the leg length. First, a previous step-climbing gait is optimized by adjusting body inclination when placing front legs on top of the step, which enables RHex with different sizes to perform the rising stage of the gait. Second, to improve the climbing heights, a novel quasi-static climbing gait is proposed by using the reversed claw-shape legs to reach the higher step. The nondeformable legs are used to raise the center of mass (COM) of the body by lifting the front and rear legs alternately so that the front legs can reach the top of the step, then the front and middle legs are lifted alternately to maneuver COM up onto the step. The simulations and dynamic analysis of climbing steps are utilized to verify the feasibility of the improved gait. Finally, the step-climbing experiments at different heights are performed with the optimized gaits to compare with the existing gaits. The results of simulations and experiments show the superiority of the proposed gaits due to climbing higher steps.     

Study on mobile mechanism of a climbing robot for stair cleaning: a translational locomotion mechanism and turning motion

In human living environments, it is often the case that the cleaning area is three-dimensional space such as a high-rise building. An autonomous cleaning robot is proposed so as to move on all floors including stairs in a building. When a robot cleans in three-dimensional space, it needs to turn for direction in addition to climb down stairs. The proposed robot selects movement using legs or wheels depending on stairs or flat surfaces. In this paper, a mobile mechanism and a control method are described for translational locomotion. The translational mechanism is based on using two-wheel-drive type omni-directional mobile mechanism. To recognize a stair using the position-sensitive detector, the robot shifts from translational locomotion to climbing down motion or edge-following motion. It is shown that the proposed robot turns to face a stair with the accuracy of 5°.     

轮腿式微型机器人系统研究

轮腿复合式机器人是在轮式机器人的基础上,通过优化轮子设计以达到快速灵活运动的一种新型的地面移动系统。该机器人主体由机架、两条主轴、齿轮减速机构、轮腿复合机构组成,由单电机驱动,控制系统相对简单。该机器人相比于普通轮式机器人具有较强的越障能力,且结构精简、体积小、重量轻。采用ADAMS对该机器人进行了运动学和动力学仿真,详细探讨了其越障能力、安装相位、轮腿结构、步态等关键问题,为其物理样机的设计、优化和控制提供了理论依据。     

Design and manufacturing a novel screw-in-pipe inspection robot with steering capability

In this article, a novel in-pipe inspection robot is designed and manufactured in Kharazmi University KharazmPipeBot. This robot is able to move through any pipeline with a predefined diameter range with a variable pitch rate and report any desired data within the pipe with the aid of the installed camera. To achieve the highest stability of the robot through the pipe, the robot's movement is based on the screw locomotion protocol provided by the aid of its rotor and stator. A simple suspension is designed for three legs of the robot by installing a passive prismatic joint equipped with a spring for each leg to provide a smoother movement for the robot chassis. The main novelty of the robot is adding an extra controlling actuator for the robot which is the steer of the front wheels. This input can control the pitch rate of the robot movement and consequently the spiral track of the wheels can be actively managed. This importance lets us to bypass the probable obstacles attached to the inner wall of the pipes. A brief presentation of the robot model is delivered. Afterward, to verify the claimed novelties of the system, a prototype of the robot is manufactured in Kharazmi University and the efficiency of the robot is demonstrated by conducting some initial experimental tests. It is shown that the robot can move with a variable pitch rate through the wall and pass a detected obstacle accordingly.     

Stability Analysis of a Wheel-Track-Leg Hybrid Mobile Robot

This paper proposes a new wheel-track-leg hybrid robot. The hybrid robot comprises a robot body, four driving mechanisms, four independent track devices, two supporting legs and one wheel lifting mechanism, which can fully benefit different advantages from wheeled, tracked and legged robots to adapt itself to varied landforms (the rough terrain and high obstacle). Based on the symmetrical mechanical structure, locomotion modes of the mobile robot are analyzed. With the coordinate transformation matrix, the center of mass of the robot is described. Moreover, the stability pyramid method is used to analyze on the climbing motion, especially in the hybrid locomotion mode. Through theoretical analysis, simulation and experimental verification, it’s proven that the robot can remain stable in the process of climbing motion.     

Optimal design of a stair-climbing mobile robot with flip mechanism

Stairs overcoming is a primary challenge for mobile robots moving in human environments, and the contradiction between the portability and the adaptability of stair climbing robot is not well resolved. In this paper, we present an optimal design of a flip-type mobile robot in order to improve the adaptability as well as stability while climbing stairs. The kinematic constraints on the flip mechanism are derived to prevent undesired interferences among stairs, wheels and main body during climbing stairs. The objective function is proposed according to the traction demand of the robot during stair-climbing motion for the first time and the value of the objective function is calculated though kinetic analysis. The Taguchi method is using as the optimization tool because of its simplicity and cost-effectiveness both in formulating an objective function and in satisfying multiple constraints simultaneously. The performance of the robot under the optimal parameters is verified through simulations and experiments.     

桥梁缆索检测蛇形机器人攀爬运动分析与实现

为方便实现对桥梁缆索的检测和日常维护任务,利用蛇形机器人良好的适应性,通过研究其控制规律,给出了一种简单的并可实现蛇形机器人沿缆索进行螺旋攀爬运动的控制函数.分析了螺旋攀爬运动中控制参数与螺旋参数之间的关系,利用粒子群优化算法对控制参数与螺旋半径、螺旋上升角、螺距之间的关系进行优化拟合,给出了拟合函数.通过Webots...     

Obstacle avoidance of snake robot by switching control constraint

In this paper, we propose an obstacle avoidance method for autonomous locomotion control of a snake robot. The snake robot consists of rigid links, active joints and passive wheels, and can move only by varying its shape. The pass planning for the obstacle avoidance is a complicated problem because the snake robot has many states, control inputs and the under-actuated property. In our proposed method, the snake motion is restricted to a periodic undulate curve (called a serpenoid curve) by an additional control constraint and the undulate curve is tuned by switching the control constraint in order that the snake robot avoids the obstacle. Therefore, the path planning is simplified and the snake robot will achieve the obstacle avoidance with an efficient path. In this paper, we denote the details of our method and investigate the effectiveness of our strategy by numerical simulations.     

Equilibrium analysis of multi-limbs walking and climbing robots

The paper discusses the complex problem of assessing online the static equilibrium of statically-indeterminate climbing and walking robots (CLAWARs) with quasi-static locomotion. The method proposed is general and works for whatever number of legs and ropes operated by actuated winches connecting the robot to the environment. The configuration of the robot is assigned. First, the compliance of the robot body, of the legs and the compliances of the ground and the ropes are modeled as localized elasticities. The static equilibrium problem of the resulting model is statically-determinate under the hypothesis that the foot and rope points (where the ropes are fixed to the robot body) are joined to the ground by bilateral constraints. Since these constraints are unilateral (the feet are contact points and can detach from the ground, and the ropes can become slack), it is necessary to apply an iterative solving procedure in order to solve the static equilibrium problem. The method presented in the paper is a fast and effective alternative to nonlinear analysis of a finite element model of the robot at any assigned configuration. As an example, we consider the case of the heavy-duty CLAWAR Roboclimber.     

A control for an insectomorphic robot in motion along a vertical corner and a horizontal beam

The problems of climbing a vertical corner and of moving on a horizontal beam while maintaining dynamic balance are solved for a six-legged robot. The opening angle of the comer is equal to Gp/2, and robot climbs it from a horizontal supporting surface. The motion is implemented using dry friction forces. The motion pattern in the passage from the horizontal surface on the corner and the motion in the upward direction are determined by the structure of the gallop gait. Using computer simulation, it is shown that a friction coefficient equal to 1.1 is sufficient for implementation of the motion constructed. In the motion on a narrow beam, the robot goes by a diagonal gait on the front and back legs. The middle legs are used as fly wheels in order to control the kinetic moment of the body relative to the supporting diagonal to reach robot stability in the top position. A PD-controller is designed that provides the required control of the relative motion of the middle legs. The results of computer simulation of the controlled robot dynamics are presented.     

Planar legged walking of a passive-spine hexapod robot

This paper proposes a new legged walking method for a novel passive-spine hexapod robot. This robot consists of several body segments connected by passive body joints. Each of the body segments carries two 1-DoF (degree of freedom) actuated legs. The robot is capable of achieving planar legged walking by rapidly abducting and adducting its legs. To model the mobility of a robot based on this simple design, the candidate configurations from all possible configurations are first selected in a mobility analysis of the robot based on the screw theory. All the feasible sequences of these candidate configurations are then searched to form planar locomotion gaits. Next, locomotive performance of the gaits is analyzed. Finally, the proposed locomotion design and gait planning methods are verified through simulations and experiments.     

Design and analysis of a wall-climbing robot for passive adaptive movement on variable-curvature metal facades

To facilitate the safe adsorption and stable motion of robots on curved metal surfaces, a wall-climbing robot with a wheeled-type mobile mechanism that can passively self-adapt to walls with different curvature is proposed. The robot is composed of two relatively independent passive adaptive mobile mechanisms and overrunning permanent magnetic adsorption devices to achieve effective fitting of the driving wheels to the wall surface and adaptive surface motion. The overall design is based on a double-hinged connection scheme and gap-type permanent magnetic adsorption. The minimum adsorption force required for the robot to achieve stable climbing motion with no risk of slipping or capsizing is determined by developing a static analysis model. The effects of air-gap size and wall thickness on the adsorption force are analyzed by means of magnetic circuit design studies and parametric simulations on the permanent magnet adsorption device, as well as design optimization of the permanent magnet device. The motion performance test of the fabricated prototype shows that the robot can achieve adaptive curvature motion with self-attitude adjustment, and has a certain load capacity, obstacle crossing capability, and good surface adaptivity.     

On the Improvement of Walking Performance in Natural Environments by a Compliant Adaptive Gait

It is a widespread idea that animal-legged locomotion is better than wheeled locomotion on natural rough terrain. However, the use of legs as a locomotion system for vehicles and robots still has a long way to go before it can compete with wheels and trucks, even on natural ground. This paper aims to solve two main disadvantages plaguing walking robots: their inability to react to external disturbances (which is also a drawback of wheeled robots); and their extreme slowness. Both problems are reduced here by combining: 1) a gait-parameter-adaptation method that maximizes a dynamic energy stability margin and 2) an active-compliance controller with a new term that compensates for stability variations, thus helping the robot react stably in the face of disturbances. As a result, the combined gait-adaptation approach helps the robot achieve faster, more stable compliant motions than conventional controllers. Experiments performed with the SILO4 quadruped robot show a relevant improvement in the walking gait     

基于能量的蛇形机器人蜿蜒运动控制方法的仿真与实验研究

能量作为最基本的物理量之一, 联系着蛇形机器人蜿蜒运动的各个方面. 能量耗散描述了环境交互作用, 能量转换对应着运动的动力学过程, 能量平衡反映了蜿蜒运动的协调性. 提出一种基于能量的蛇形机器人蜿蜒运动控制方法-被动蜿蜒. 通过输出关节力矩控制机器人蜿蜒运动, 由机器人的能量状态调整力矩的大小. 仿真结果显示了被动蜿蜒控制下机器人的构形、角度、力矩、能量状态和转弯特性, 并对控制力矩进行了递归分析. 基于Optotrak运动测量系统构建了被动蜿蜒控制的模拟/物理混合实验系统. 进行了移动实验和拖动实验, 前者改变环境的摩擦特性,后者改变机器人的负载. 仿真和实验验证了蛇形机器人被动蜿蜒控制的有效性和适应性.     

基于旋转电弧传感的新型轮式自主移动焊接机器人系统

介绍了一种基于旋转电弧传感的新型轮式焊接机器人系统，机构上前轮采用步进电机转向，后轮由交流伺服电机驱动，左右与上下十字滑块用两个直流伺服电机控制，这4个电机用一4轴驱动运动控制器进行驱动控制，大大提高了集成度与控制效率，目前是一种新型的焊接自动化装备．     

Bio-inspired design and movement generation of dung beetle-like legs

African ball-rolling dung beetles can use their front legs for multiple purposes that include walking, manipulating or forming a dung ball, and also transporting it. Their multifunctional legs can be used as inspiration for the design of a multifunctional robot leg. Thus, in this paper, we present the development of real robot legs based on the study of the front legs of the beetle. The leg movements of the beetle, during walking as well as manipulating and transporting a dung ball, were observed and reproduced on the robot leg. Each robot leg consists of three main segments which were built using 3D printing. The segments were combined with four active joints in total (i.e., 4 degrees of freedom) to mimic the leg movements of the beetle for locomotion as well as object manipulation and transportation. Kinematics analysis of the leg was also performed to identify its workspace. The results show that the robot leg is able to perform all the movements with trajectories comparable to the beetle leg. To this end, the study contributes not only to the design of novel multifunctional robot legs but also to the methodology for bio-inspired leg design.     

Energy Consumption Optimization for Mobile Robots Motion Using Predictive Control

Operation of mobile robots in off-road environment requires the attention to the torque saturation problem that occurs in the wheels DC motors while climbing hills. In the present work, off-road conditions are utilized to benefit while avoiding torque saturation. Energy optimization algorithm using predictive control is implemented on a two-DC motor-driven wheels mobile robot while crossing a ditch. The predictive control algorithm is simulated and compared with the PID control and the open-loop control. Predictive control showed more capability to avoid torque saturation and noticeable reduction in the energy consumption. Furthermore, using the wheels motors armature current instead of the supply voltage as control variable in the predictive control showed more efficient speed control. Simulation results showed that in case of known ditch dimensions ahead of time, the developed algorithm is feasible. Experimental examination of the developed energy optimization algorithm is presented. The experimental results showed a good agreement with the simulation results. The effects of the road slope and the prediction horizon length on the consumed energy are evaluated. The analytical study showed that the energy consumption is reduced by increasing the prediction horizon until it reaches a limit at which no more energy reduction is obtained. This limit is proportional to the width of the ditch in front of the mobile robot. Curve fitting is applied to the obtained results to address further the effect of the parameters on the energy consumption.     

A unified dynamic algorithm for wheeled multibody systems with passive joints and nonholonomic constraints

This paper presents a systematic approach to develop a generalized symbolic/numerical dynamic algorithm for modeling and simulation of multibody systems with branches and wheels. The proposed dynamic algorithm includes the direct kinematic and inverse dynamic models of the wheeled systems with prismatic/revolute as well as actuated/passive degrees of freedom. Using the geometric configuration of the system through modified Denavit–Hartenberg convention, symbolic equations in general algorithmic form are developed for kinematic constraints associated with the wheel–ground contacts. The Newton–Euler equations are used to develop an algorithm for the inverse dynamic model of the multibody system. The complete algorithm is then used to solve the kinematics and dynamics of the system, and computes: (i) the kinematics of the external/internal passive degrees of freedom of the system, (ii) the Lagrange multipliers associated with the wheel–ground contacts, and (iii) the driving forces/torques of the actuated degrees of freedom. Some examples are solved with the help of the proposed algorithm, using MATLAB, to illustrate its implementation on different wheeled systems. These examples include a differential wheeled robot, a snake-like wheeled system, and a bicycle.