Showing papers by "Yili Fu published in 2019"

Kinematic calibration of serial robot using dual quaternions

Abstract: The purpose of this paper is to propose an error model for serial robot kinematic calibration based on dual quaternions.,The dual quaternions are the combination of dual-number theory and quaternion algebra, which means that they can represent spatial transformation. The dual quaternions can represent the screw displacement in a compact and efficient way, so that they are used for the kinematic analysis of serial robot. The error model proposed in this paper is derived from the forward kinematic equations via using dual quaternion algebra. The full pose measurements are considered to apply the error model to the serial robot by using Leica Geosystems Absolute Tracker (AT960) and tracker machine control (T-MAC) probe.,Two kinematic-parameter identification algorithms are derived from the proposed error model based on dual quaternions, and they can be used for serial robot calibration. The error model uses Denavit–Hartenberg (DH) notation in the kinematic analysis, so that it gives the intuitive geometrical meaning of the kinematic parameters. The absolute tracker system can measure the position and orientation of the end-effector (EE) simultaneously via using T-MAC.,The error model formulated by dual quaternion algebra contains all the basic geometrical parameters of serial robot during the kinematic calibration process. The vector of dual quaternion error can be used as an indicator to represent the trend of error change of robot’s EE between the nominal value and the actual value. The accuracy of the EE is improved after nearly 20 measurements in the experiment conduct on robot SDA5F. The simulation and experiment verify the effectiveness of the error model and the calibration algorithms.

Leg Trajectory Planning for Quadruped Robots with High-Speed Trot Gait

Abstract: In this paper, a single leg platform for quadruped robots is designed based on the motivation of high-speed locomotion. The leg is designed for lightweight and low inertia with a structure of three joints by imitating quadruped animals. Because high acceleration and extensive loadings will be involved on the legs during the high-speed locomotion, the trade-off between the leg mass and strength is specifically designed and evaluated with the finite element analysis. Moreover, quadruped animals usually increase stride frequency and decrease contact time as the locomotion speed increases, while maintaining the swing duration during trot gait. Inspired by this phenomenon, the foot-end trajectory for quadruped robots with a high-speed trot gait is proposed. The gait trajectory is planned for swing and stance phase; thus the robot can keep its stability with adjustable trajectories while following a specific gait pattern. Especially for the swing phase, the proposed trajectory can minimize the maximum acceleration of legs and ensure the continuity of position, speed, and acceleration. Then, based on the kinematics analysis, the proposed trajectory is compared with the trajectory of Bezier curve for the power consumption. Finally, a simulation with Webots software is carried out for verifying the motion stability with two trajectory planning schemes respectively. Moreover, a motion capture device is used for evaluating the tracking accuracy of two schemes for obtaining an optimal gait trajectory suitable for high-speed trot gait.

A Telepresence System for Therapist-in-the-Loop Training for Elbow Joint Rehabilitation

Abstract: This paper proposes a new robotic rehabilitation training platform that is motivated by the requirement for adjusting the training strategy and intensity in a patient-specific manner. The platform is implemented for tele-rehabilitation and is comprised of a haptic device operated by therapists, a lightweight exoskeleton worn by patients and a visually shared model. Through the visually shared model, the motion of the therapist and patient are measured and mapped to the motion of the corresponding object. Thus, the force generated by the therapist can be transferred to the patient for delivering training, while real-time force feedback with high transparency can be provided to the therapist so they know the amount of force being applied to patients in real time. In particular, both assistive therapy in the early stages and resistive therapy in the later stages of stroke can be performed. The home-use exoskeleton device is specifically designed to be light-weight and compliant for safety. The patient-exoskeleton and therapist-haptic interaction performance is evaluated by observing the muscle activities and interaction force. Two volunteers were requested to imitate the process of the therapist-in-the-loop training to evaluate the proposed platform.

An enhanced pose tracking method using progressive scan matching

Abstract: The purpose of this paper is to propose an enhanced pose tracking method using progressive scan matching, focusing on accuracy, time efficiency and robustness.,The general purpose of localization algorithms is to dynamically track a robot instead of globally locating one. In this paper, progressive scan matching is used to promote the performance of pose tracking. Rotational and translational samples are separately generated to accelerate the calculation and to increase the accuracy. Progressive iteration of sample generation can ensure localization to achieve a specific precision. The direction of localization uncertainty is taken into consideration to increase robustness. Nonlinear optimization is adopted to achieve a more precise result.,The proposed method was implemented on a self-made mobile robot. Two experiments were conducted to test the accuracy and time efficiency of the method. The comparison with the basic Monte Carlo localization shows the advantages of the method. Another two experiments were conducted to test the robustness of the method. The result shows that the method can relocate a robot from an inaccurate place if the offset is moderate.,An enhanced pose tracking method is proposed to promote the performance by separately processing rotational and translational samples, progressively iterating the sample generation, taking the direction of localization uncertainty into consideration and adopting nonlinear optimization. The proposed method enables a robot to accurately and quickly locate itself in the environment with robustness.

Wheel leg type humanoid robot with internal oil flowing

Abstract: The invention discloses a wheel leg type humanoid robot with internal oil flowing, relates to the technical field of robots, and aims to solve the problems that when a hydraulic driving unit and a power unit are connected by adopting a rubber hose, the hose is long, the pipe arrangement is complex, and the movement flexibility of a conventional hydraulically-driven robot is influenced. The humanoid robot comprises a head, shoulders, a body, a hip pelvic bone, a first hydraulic connecting rod assembly, a second hydraulic connecting rod assembly, a third hydraulic connecting rod assembly, a hydraulic cylinder, two mechanical arms, two thighs, two shanks and two driving wheels. The head, the shoulders and the body are sequentially and fixedly connected together from top to bottom; the body ishinged to the hip pelvic bone and driven by the hydraulic cylinder, each mechanical arm is hinged to the corresponding shoulder and driven by the first hydraulic connecting rod assembly to swing leftwards and rightwards, and each thigh is hinged to the hip pelvic bone and driven by the second hydraulic connecting rod assembly to swing forwards and backwards. Each joint adopts a hose-free oil way,so that the pipeline abrasion fault is greatly reduced, and the safety and the reliability of the whole machine are improved.

A novel obstacle avoidance method based on multi-information inflation map

Abstract: This paper aims to provide a novel obstacle avoidance method based on multi-information inflation map.,In this paper, the multi-information inflation map is introduced, which considers different information, including a two-dimensional grid map and a variety of sensor information. The static layer of the map is pre-processed at first. Then sensor inputs are added in different semantic layers. The processed information in semantic layers is used to update the static layer. The obstacle avoidance algorithm based on the multi-information inflation map is able to generate different avoidance paths for different kinds of obstacles, and the motion planning based on multi-information inflation map can track the global path and drive the robot.,The proposed method was implemented on a self-made mobile robot. Four experiments are conducted to verify the advantages of the proposed method. The first experiment is to demonstrate the advantages of the multi-information inflation map over the layered cost map. The second and third experiments verify the effectiveness of the obstacle avoidance path generation and motion planning. The fourth experiment comprehensively verifies that the obstacle avoidance algorithm is able to deal with different kinds of obstacles.,The multi-information inflation map proposed in this paper has better performance than the layered cost maps. As the static layer is pre-processed, the computational efficiency is higher. Sensor information is added in semantic layers with different cost attenuation coefficients. All layers are reset before next update. Therefore, the previous state will not affect the current situation. The obstacle avoidance and motion planning algorithm based on the multi-information inflation map can generate different paths for different obstacles and drive a robot safely and control the velocity according to different conditions.

Energy accumulator auxiliary power jumping leg

Abstract: The invention discloses an energy accumulator auxiliary power jumping leg and relates to the ethical field of a hydraulically driven robot. The problem that an existing hydraulically driven joint legis difficult to realize great height jumping and is insufficient in hydraulic power system power and low in jumping energy utilization efficiency is solved. According to the jumping leg, two ends of ahip joint shaft are rotationally connected with an inner thigh plate and an outer thigh plate; one end of a hip joint two-force bar is rotationally connected with a side wall of the knee joint shaft;an upper calf is rotationally connected with the inner thigh plate and the outer thigh plate through utilization of a knee joint shaft; one end of a knee joint two-force bar is rotationally connectedwith the upper calf through utilization of a calf two-force bar shaft; a tail end of a piston rod of a calf hydraulic cylinder is connected with a slide block connection element on a guide rail; theslide block connection element on the guide rail is connected with the other end of the knee joint two-force bar; the tail end of the piston rod of a thigh hydraulic cylinder is connected with the slide block connection element on the guide rail; and the slide block connection element on the guide rail is connected with the other end of the hip joint two-force bar. The jumping leg is used for thehydraulically driven joint leg to realize great height jumping.

Hose-free internal oil circuit for hydraulic wheel-legged humanoid robot

Abstract: The invention discloses a hose-free internal oil circuit for a hydraulic wheel-legged humanoid robot, relates to the technical field of humanoid robots, and aims at solving the problems of easy wear, redundant pipeline and inconvenient disassembly and assembly of an existing external hydraulic oil circuit. The head and shoulders, mechanical arms, a body, hip pelvic pone, thighs and shanks of the hydraulic wheel-legged humanoid robot are all of framework structures with hydraulic oil circuit cavity assemblies; an oil inlet and an oil return port are formed in the rear side back of the body; the oil inlet end of the oil inlet is connected with an external hydraulic power system through a hydraulic oil circuit; the oil outlet end of the oil return port is connected with the external hydraulic power system through the hydraulic oil circuit. The hose-free internal oil circuit disclosed by the invention is used for the humanoid robot.

Miniaturized onboard hydraulic servo backpack

Abstract: The invention discloses a miniaturized onboard hydraulic servo backpack, and relates to the technical field of airborne hydraulic oil sources. The invention aims to solve the problems that an existing external hydraulic oil source limits the movement range of a machine, and an airborne oil source is large in noise and low in efficiency. The low-pressure output port of a load is connected with the input end of an oil return pipeline, the output end of the oil return pipeline is connected with an inlet of a first gear pump, an outlet of the first gear pump is connected with the input end of an oil liquid output pipeline, the output end of the oil liquid output pipeline is simultaneously connected with the high-pressure input port of the load and the input end of the oil return pipeline, a system sensing module is used for acquiring the rotating speed of a motor, the flow of oil liquid in the oil liquid output pipeline, the pressure of the oil liquid in the oil liquid output pipeline and the temperature of the oil liquid, and collected information is transmitted to a driving control module; and the driving control module is used for adjusting the pressure and the flow of the output oil liquid by controlling the pressure regulating and filtering module. The hydraulic servo backpack is used for carrying out hydraulic control on the oil liquid entering the load.