Dengpeng Xing

Arm/trunk motion generation for humanoid robot

This paper develops two motion generation methods for the upper body of humanoid robots based on compensating for the yaw moment of whole body during motion. These upper body motions can effectively solve the stability problem of feet spin for robot walk. We analyze the ground reactive torque, separate the yaw moment as the compensating object and discuss the effect of arms swinging on whole body locomotion. By taking the ZMP as the reference point, trunk spin motion and arms swinging motion are generated to improve the biped motion stability, based on compensating for the yaw moment. The methods are further compared from the energy consumption point of view. Simulated experimental results validate the performance and the feasibility of the proposed methods.

Gain scheduled control of perturbed standing balance

This paper develops full-state parametric controllers for standing balance of humanoid robots in response to impulsive and constant pushes. We also explore a hypothesis that postural feedback gains in standing balance should change with perturbation size. From an engineering point of view this is known as gain scheduling. We use an optimization approach to see if feedback gains should scale with the perturbation for a simulated robot. We simulate models in the sagittal and lateral plane and in 3-dimensions, use a horizontal push of a given size, direction and location as a perturbation, and optimize parametric controllers for different push sizes, directions and locations. During a simulated perturbation experiment, the appropriate controller is continuously selected based on the current push. For an impulse, the simulated robot recovers back to the initial state; for a constant push, the robot moves to an equilibrium position which leans into the push and has zero joint torques. We show the performance of optimized parametric controllers in response to different external pushes.

Coordinated Insertion Control for Inclined Precision Assembly

This paper proposes a hybrid control strategy to coordinate inclined insertion for precision assembly, in order to increase the capability of dealing with disturbances. Precision assembly requires accurate manipulation, while due to perturbations, objects may be initiated with deviated posture and hold this deviation during insertion. To improve the assembly robustness to inclination, we develop a coordination structure: compensational motions for the mismatch between inclined posture and insertion direction by using kinematics and image Jacobian matrix methods; contact force acquisition to handle the indirect posture measurement between force sensor and inclined object, by taking advantage of the microimaging characteristics; and a hybrid coordinated insertion strategy to deal with the insufficient degree-of-freedom (DOF) allocation on each arm, applicable for assemblies in interference fit or clearance fit. Experiments are carried out to demonstrate the effectiveness of the proposed methods.

Multiple Balance Strategies for Humanoid Standing Control

Full-state feedback parametric controllers are proposed for standing balance of humanoid robots in response to impulsive and constant pushes. Multiple robot models are used to approach multiple strategies in human standing balance. For each model, we design a parametric controller acting on each state variable and optimize controller parameters for different push sizes, directions, and locations. The performance of each controller is shown in response to different external pushes. By comparing the capabilities of handling disturbances in each strategy, the contributions of every joint to standing balance are also explored.

Precision Assembly Among Multiple Thin Objects With Various Fit Types

This paper investigates precision assembly combining several subprocesses on a platform with multiple robot arms. The task manipulates irregular objects and incorporates interference and clearance assemblies. We use a mechanism with six robot arms and three microscopes to fulfill this assignment, and propose a general control strategy to attain high precision and protect objects. System calibration includes the image Jacobian matrix to connect Cartesian motion with the image movement and force transformation matrix to relate between coordinates of force sensor and manipulators. In the control structure, a general strategy is proposed for assembly with multiple manipulators, in which we present an assembly plan module to generate desired states of each object by using an optimization approach, design a method to determine the collision when blocking, and propose a hybrid control scheme for both contact and clearance assembly controllers. Experiments are carried out to demonstrate the validation of the proposed methods.

Active calibration and its applications on micro-operating platform with multiple manipulators

The microscope has characteristics of a planar vision with small view field and small view depth. For micro operation systems with multiple manipulators, the handling of irregular objects may lead to a nonorthogonal microscopic system, which needs to focus on clear viewing interested features, and it may also hardly locate the exact position and posture of the robot arms. In view of these, this paper proposes an active calibration method to compute image Jacobian matrix, which maps from the relative motion of the manipulators to the image coordination changes in the microscopes. We also investigate the applications in micro operator positioning, tracking for distributed systems, and movement optimization in micro-assembly. Experiments are carried out on a micro-assembly platform equipped with three microscopes and six robot arms, and the results validate the effectiveness of the proposed method.

Motion generation for the upper body of humanoid robot

This paper presents two motion generation methods for the upper body of the humanoid robot in order to guarantee the equilibrium condition of the yaw moment in bipedal planning based on the ZMP convention. The reactive torque from the ground and the effect of arms swinging on robots body locomotion are analyzed. Therefore trunk spin motion and arms swinging motion are planned to improve the motion stability of the robot, based on compensating for the yaw moment. These two methods are further compared with each other from the viewpoint of energy consumption. Simulation results evaluate the performance and the feasibility of the proposed methods.

A sequence of micro-assembly for irregular objects based on a multiple manipulator platform

Difficulties arise in the micro-assembly of many irregular objects and in the insertion with contact between components of soft materials. To handle these problems, we design a micro-operational platform with multiple manipulators to facilitate a sequence of assembly. Six robot arms and three microscopes are incorporated, together with macro and micro motion systems. We also propose a hybrid control strategy to achieve high precision and protect objects. This hybrid scheme includes vision based positioning controllers for alignment, which employ incremental PI controllers and image Jacobian matrix, force based controllers for insertion, and a decision mechanism determining the assembly state. Experiments demonstrate the effectiveness of the proposed platform and control methods.

Motion Control for Cylindrical Objects in Microscope's View Using a Projection Method— I: Collision Detection and Detach Control

This paper investigates collision detection between cylindrical or cylinder-enveloped components when mutual blocking occurs in the view of microscopes and detach control to separate objects if contact occurs. We use a projection method to convert two microscopic views to contours on a projection plane and to detect high-dimensional collision by studying the projections relationships in low dimension. Eleven cases are totally categorized and 12 parameters are constructed for detection on the basis of relative postures and positions. Furthermore, we present a detach controller to handle with object contact according to collision status, objects’ main axis, and the computed contact position. Simulations and experiments are carried out to demonstrate the validity of the proposed method.

Collision detection for blocking cylindrical objects

This paper proposes two methods for collision detection between cylindrical components when mutual blocking occurs in the view of cameras. In reconstruction approach, 3D models are built according to key features captured by cameras and constraint optimization is employed to rapidly find possible intersections. To satisfy the computational efficiency required by real time operation, we present another way, projection method, to convert two planar views to contours on a projection plane and to detect high dimension collisions by studying the projections relationships in low dimension. Nine cases are totally categorized and eleven parameters are constructed for detection on the basis of relative postures and positions. Simulations and experiments are carried out to demonstrate their validity.