Joint Trajectory Planning of Space Modular Reconfigurable Satellites Based on Kinematic Model

This paper investigates the application of particle swarm optimization (PSO) algorithm to plan joint trajectories of the space modular reconfigurable satellite (SMRS). SMRS changes its configuration by joint motions to complete various space missions; its movement stability is affected by joints motions because of the dynamic coupling effect in space. To improve the movement stability in reconfiguration progress, this paper establishes the optimization object equation to characterize the movement stability of SMRS in its reconfiguration process. The velocity-level and position-level kinematic models based on the proposed virtual joint coordinate system of SMRS are derived. The virtual joint coordinate system solves the problem of asymmetric joint coordinate system resulted by the asymmetric joint arrangement of SMRS. The six-order and seven-order polynomial curves are chosen to parameterize the joint trajectories and ensure the continuous position, velocity, and acceleration of joint motions. Finally, PSO algorithm is used to optimize the trajectory parameters in two cases. Consistent optimization results in terms of the six-order and seven-order polynomial in both cases prove the PSO algorithm can be effectively used for joint trajectory planning of SMRS.

Analysis and Optimization of Interpolation Points for Quadruped Robots Joint Trajectory

Trajectory planning is the foundation of locomotion control for quadruped robots. This paper proposes a bionic foot-end trajectory which can adapt to many kinds of terrains and gaits based on the idea of trajectory planning combining Cartesian space with joint space. Trajectory points are picked for inverse kinematics solution, and then quintic polynomials are used to plan joint space trajectories. In order to ensure that the foot-end trajectory generated by the joint trajectory planning is closer to the original Cartesian trajectory, the distributions of the interpolation point are analyzed from the spatial domain to temporal domain. An evaluation function was established to assess the closeness degree between the actual trajectory and the original curve. Subsequently, the particle swarm optimization (PSO) algorithm and genetic algorithm (GA) for the points selection are used to obtain a more precise trajectory. Simulation and physical prototype experiments were included to support the correctness and effectiveness of the algorithms and the conclusions.

Joint Trajectory Planning Based on Minimum Euclidean Distance of Joint Angles of a Seven-Degrees-of-Freedom Manipulator for a Sequential Reaching Task

When a nuclear power disaster occurs at a nuclear power plant, it is hazardous for humans to enter the plant. If robots could remove radioactive substances adhering to a plane such as a plant wall, humans would be able to enter the plant to investigate the situation and to work. In this study, to efficiently remove radioactive substances from a wall with a manipulator, we examined joint trajectory planning based on the minimum Euclidean distance of joint angles of a seven-degrees-of-freedom (7-DOF) serial link manipulator for a sequential reaching task on a plane. We demonstrate the planning for the sequential reaching task, which is an iterative point-to-point reaching movement between positions on a plane. The joint angles for each target position were obtained based on the inverse kinematics for an arm angle, and the optimal arm angles within the constraints of the joint angles were computed by the sequential quadratic programming method. The optimal trajectories for the arm angles were compared with the trajectories of the joint angles that were the eight inverse kinematic solutions for a fixed arm angle. The result showed that through optimal planning, an efficient trajectory within the movable ranges of the joint angles could be obtained for the sequential reaching task.

Motion Planning of Redundant Manipulators for Painting Uniform Thick Coating in Irregular Duct

The paper presents a motion planning method of redundant manipulator for painting uniform thick coating on the interior of irregular duct of some aircrafts. Discontinuous peripheral painting method is employed by analyzing the restrictions during painting the duct. For improving the longitudinal uniformity of thick coating, the interlacing painting method plans two sets of sweeping paths and an interlacing distance between the starting paths of the two times of painting. The interlacing distance and overlapping distance are optimized by establishing and analyzing the model of longitudinal uniformity. To enhance the transverse uniformity, sweeping speeds for curved surfaces are calculated by the ratio of transfer efficiency after the basic sweeping speed for the plane is determined. The intertwining method, minimizing the sum of the weighed distances between the duct centerline and key points of the manipulator links, is employed for the joint trajectory planning without collision. The simulation and experiment results show that the redundant manipulators can finish painting the internal surface of the irregular S-shaped duct without collision. The maximum relative deviation is 16.3% and the thicknesses of all measurement points satisfy the acceptance criteria of the factory.

Mechanism Configuration of Super-Redundant Robot

Structural synthesis of super-redundant mechanism is a key to design of painting robot for S-shape duct. Based on the principles of modular structure design, the painting robot for S-shape duct falls naturally into three separate control and design components: a moving platform, a locating mechanism, and a painting manipulator. The moving platform consists of a robot body, wheels, gasbags for position adjustment, and screw jacks. The 3PR-type serial mechanism is adopted for location. The super-redundant 3P7R-type serial mechanism is used for the painting manipulator. The restriction of the distance between connecting rods and the axis of the duct is employed to control self-motion of the painting manipulator for joint trajectory planning. Experiment result shows that minimal distance between robot joints and duct interior is 18mm and that average dynamic accuracy is ±6.8mm, which satisfies the working requirements.

Analysis of Take-Off Performances for a Double-Joint Hopping Leg

The paper is focused on a double-joint hopping leg driven by motors. Using relative coordinates, its kinematics and dynamics between the system and components are established during the launching stage of jumping, and the take-off mechanism is analyzed. Based on mechanics of jump movement and joint trajectory planning method, the impact of the change of the system initial posture and joint trajectories upon the system take-off performances, such as energy efficiency, instantaneous velocity of the system center of mass (CoM), is discussed by using numerical simulation approach with drive constraints. For a hopping robot, good take-off performances can improve its motion ability, so the resulted conclusions here provides a useful and helpful reference for analyzing and designing a multi-joint hopping robot.