Obstacle detection and autonomous stair climbing of a miniature jumping robot

Miniature jumping robots(MJRs)have difficulty executing autonomous movements in unstructured environments with obstacles because of their limited perception and computing resources.This study investigates the obstacle detection and autonomous stair climbing methods for MJRs.We propose an obstacle detection method based on a combination of attitude and distance detections,as well as MJRs’motion.A MEMS inertial sensor collects the yaw angle of the robot,and a ranging sensor senses the distance between the robot and the obstacle to estimate the size of the obstacle.We also propose an autonomous stair climbing algorithm based on the obstacle detection method.The robot can detect the height and width of stairs and its position relative to the stairs and then repeatedly jump to climb them step by step.Moreover,the height,width,and position are sent to a control terminal through a wireless sensor network to update the information regarding the MJR and stairs in a control interface.Furthermore,we conduct stair detection,modeling,and stair climbing experiments on the MJR and obtain acceptable precisions for autonomous obstacle negotiation.Thus,the proposed obstacle detection and stair climbing methods can enhance the locomotion capability of the MJR in environmental monitoring,search and rescue,etc.

Biological Jumping Mechanism Analysis and Modeling for Frog Robot

This paper presents a mechanical model of jumping robot based on the biological mechanism analysis of frog. By biological observation and kinematic analysis the frog jump is divided into take-offphase, aerial phase and landing phase. We find the similar trajectories of hindlimb joints during jump, the important effect of foot during take-off and the role of forelimb in supporting the body. Based on the observation, the frog jump is simplified and a mechanical model is put forward. The robot leg is represented by a 4-bar spring/linkage mechanism model, which has three Degrees of Freedom （DOF） at hip joint and one DOF （passive） at tarsometatarsal joint on the foot. The shoulder and elbow joints each has one DOF for the balancing function of arm. The ground reaction force of the model is analyzed and compared with that of frog during take-off. The results show that the model has the same advantages of low likelihood of premature lift-off and high efficiency as the frog. Analysis results and the model can be employed to develop and control a robot capable of mimicking the jumping behavior of frog.

Wheeled jumping robot by powermodulation using twisted string lever mechanism

This study introduces a wheeled robot platform with jumping ability.To realize jump movement,a twisted string lever mechanism is used,which is characterized by its compactness and variable gear ratio.Based on robot modeling and parameter calculation,the twisted string actuator shows its advantage when applied to situations such as jumping of robots,where explosiveness of output force matters.In this study,a wheeled bipedal robot equipped with the twisted string actuator is designed and fabricated.It weighs 16.0 kg and can perform jumps when it encounters obstacles.The prototype can jump up to a stage with a maximum height of 1.0 m using electric power,which is approximately 1.5 times the height of its stretched legs.

Towards Jumping Skill Learning by Target-guided Policy Optimization for Quadruped Robots

Endowing quadruped robots with the skill to forward jump is conducive to making it overcome barriers and pass through complex terrains.In this paper,a model-free control architecture with target-guided policy optimization and deep reinforcement learn-ing(DRL)for quadruped robot jumping is presented.First,the jumping phase is divided into take-off and flight-landing phases,and op-timal strategies with soft actor-critic(SAC)are constructed for the two phases respectively.Second,policy learning including expecta-tions,penalties in the overall jumping process,and extrinsic excitations is designed.Corresponding policies and constraints are all provided for successful take-off,excellent flight attitude and stable standing after landing.In order to avoid low efficiency of random ex-ploration,a curiosity module is introduced as extrinsic rewards to solve this problem.Additionally,the target-guided module encour-ages the robot explore closer and closer to desired jumping target.Simulation results indicate that the quadruped robot can realize com-pleted forward jumping locomotion with good horizontal and vertical distances,as well as excellent motion attitudes.