Chun Ta Chen

Design and fabrication of a statically stable stair-climbing robotic wheelchair

Purpose – The purpose of this paper is to present the mechanical design and stability analysis of a new stair‐climbing robotic wheelchair.Design/methodology/approach – A prototype stair‐climbing robotic wheelchair is constructed comprising a pair of rotational multi‐limbed structures pivotally mounted on opposite sides of a support base. The short arm, long arm, and triangular support structures within each rotational multi‐limbed structure rotate under the actuating effects of epicyclical gear trains.Findings – The robotic wheelchair ascends and descends stairs in a statically stable manner and has an efficient planar navigation capability.Research limitations/implications – In its current state of development, the robotic wheelchair is controlled and powered remotely via umbilical cords rather than an onboard processor and power supply.Practical implications – The robotic wheelchair provides an effective solution for enhancing the mobility of the elderly and disabled.Originality/value – The rotational m...

Optimal Path Programming of the Stewart Platform Manipulator Using the Boltzmann–Hamel–d'Alembert Dynamics Formulation Model

In this paper, the dynamics formulation of a general Stewart platform manipulator (SPM) with arbitrary geometry and inertia distribution is addressed. Based on a structured Boltzmann–Hamel–dAlembert approach, in which the true coordinates are for translations and quasi-coordinates are for rotations, a systematic methodology using the parallelism inherent in the parallel mechanisms is developed to derive the explicit closed-form dynamic equations which are feasible for both forward and inverse dynamics analyses in the task space. Thus, a singularity-free path programming of the SPM for the minimum actuating forces is presented to demonstrate the applications of the developed dynamics model. Using a parametric path representation, the singularity-free path programming problem can be cast to the determination of undetermined control points, and then a particle swarm optimization algorithm is employed to determine the optimal control points and the associated trajectories. Numerical examples are implemented for the moving platform with constant orientations and varied orientations.

Design and realization of a mobile wheelchair robot for all terrains

A novel design of a mobile wheelchair robot for all terrains, especially for staircases and inclines, is proposed. Toachieve the required locomotion, a pair of multi-limbed structures, comprised of a lift coxae, rotation femurs and support tibiae, are pivotally mounted on the opposite sides of the body and actuated to rotate through epicyclic gear trains. A dual-footing mode with a set of wheel and crawler tractors in each support tibia permits the locomotion mode depending on various terrains, and hence the mobile wheelchair robot can navigate on a flat surface, and climb up and down stairs or inclines with its body kept horizontal. The implemented design is verified experimentally using our first manufactured prototype mobile wheelchair robot and it is shown that it could be suitable for applications to wheelchairs or others.

A reflexive vehicle control architecture based on a neural model of the cockroach escape response

This paper presents a biologically inspired architecture for rapid real-time control of autonomous or semi-autonomous vehicles based on a neural model of the escape response of the American cockroach, Periplaneta americana. The architecture fuses exteroceptive and proprioceptive inputs in a manner similar to the insect to produce commands for collision avoidance and, in some cases, orientation for target strike. It functions as a reflexive subsystem that integrates smoothly with higher-level planning and behavioral control systems. The performance of the reflex is demonstrated in simulation and in hardware experiments on both air and ground vehicles, even in the presence of noisy, false or disruptive sensor data.

Singularity-free trajectory planning of platform-type parallel manipulators for minimum actuating effort and reactions

Due to the existence of singular configurations within the workspace for a platform-type parallel manipulator (PPM), the actuating force demands increase drastically as the PPM approaches or crosses singular points. Therefore, in this report, a numerical technique is presented to plan a singularity-free trajectory of the PPM for minimum actuating effort and reactions. By using the parametric trajectory representation, the singularity-free trajectory planning problem can be cast to the determination of undetermined control points, after which a particle swarm optimization algorithm is employed to find the optimal control points. This algorithm ensures that the obtained trajectories can avoid singular points within the workspace and that the PPM has the minimum actuating effort and reactions. Simulations and discussions are presented to demonstrate the effectiveness of the algorithm.

On Climbing Winding Stairs in an Open Mode for a New Robotic Wheelchair

This paper presents the mechanical design, locomotion and associated dynamic models of a new robotic wheelchair on climbing winding stairs. The prototype stair-climbing robotic wheelchair is constructed comprising a pair of rotational multi-limbed structures pivotally mounted on opposite sides of a support base so that the robotic wheelchair can ascend and descend stairs; in particular, the capability of climbing winding stairs is addressed. Based on the skid-steering analysis, the dynamic models for climbing winding stairs are developed for the trajectory planning and motion analyses. These models are required to ensure a passengers safety in such a way that the robotic wheelchair is operated in an open mode. Moreover, an equivalent constraint method is proposed for the prescribed motion of the robotic wheelchair on climbing winding stairs. The results of the simulation and maneuver are reported that show the behavior of the prototype as it climbs winding stairs in a dynamic turning.

Optimal Configuration of a Parallel Kinematic Manipulator for the Maximum Dynamic Load-Carrying Capacity

In determining the maximum dynamic load-carrying capacity (DLCC) of reconfigurable motor-driven parallel kinematic manipulators (PKM), the objective is to identify the optimal configuration which accomplishes the assigned motion for the maximum DLCC subject to the constraints imposed by the kinematics and dynamics of the manipulator structure. In this study, the maximum DLCC problem of a reconfigurable PKM is formulated using the structured Boltzmann-Hamel-dAlembert formulism, and then the optimal reconfiguration is obtained using a two-loop of optimization process, in which the particle swarm optimization (PSO) algorithm is for the outer-loop optimization and the linear programming (LP) method is for the inner-loop optimization, such that the reconfiguration is achieved by re-locating the base points along linear guide ways. The numerical results present the effects of the base locations on the DLCC and the corresponding kinematics and dynamics along the prescribed trajectory.

Enhanced development and stability analysis of a new stair-climbing robotic wheelchair

This paper reports an enhanced mechanical design and stability analysis of a new stair-climbing robotic wheelchair for the disable and elderly. The mechanism is based on a pair of rotational multi-limbed structures pivotally mounted on the opposite sides of the base. The corresponding short arm, long arm and support triangle comprising each rotational multi-limbed structure are actuated to rotate through epicyclic gear trains so that the robotic wheelchair can ascend and descend stairs in a statically stable way. Experimental results with carrying a person validate the feasibility of the proposed mechanism design and show the simplification of the associated operation process.

A skew ray tracing approach for the error analysis of optical elements with spherical boundary surfaces

This study applies a skew ray tracing approach based on a 4u2009×u20094 homogeneous coordinate transformation matrix and Snells law to analyze the errors of a rays light path as it passes through a series of optical elements with spherical boundary surfaces. The proposed error analysis methodology considers two principal sources of light path error, namely: (1) the translational errors ΔX i , ΔY i and ΔZ i and the rotational errors , and , which determine the deviation of the light path at each boundary surface, and (2) the differential changes induced in the incident point position and unit directional vector of the refracted/reflected ray as a result of differential changes in the position and unit directional vector of the light source. The validity of the proposed methodology is verified by analyzing the effects of optical errors in a solid glass cats eye.

The effects of ultrasonic vibration on mechanical properties of tungsten particle-reinforced copper-matrix composites

ABSTRACT W-Cu micro-powder mixtures usually have poor sinterability due to the relatively low solubility of W in both solid and liquid Cu. In fabricating W-Cu composites, an electroless copper plating process is often used to coat Cu on the W particle surface prior to the sintering process. Due to their small size W particles tend to agglomerate during the plating process, hence the individual particle may not be properly coated with Cu. In this study, ultrasonic vibration is applied in the electroless plating process to break up the agglomerations and restrain the powders from gathering, ensuring a uniform deposition of the Cu on individual W particle. W-Cu composite samples containing pure Cu and 6, 9 and 12 wt-% of Cu-coated W particles, respectively, are fabricated using a standard powder metallurgy technique. It is shown that the application of ultrasonic vibration in the activation and deposition steps of the electroless copper plating process prevents W powder agglomeration and ensures that each W particle is coated with Cu. As a result, the mechanical properties of the W-Cu composites are significantly improved. It is found that the optimal tensile strength and yield strength are obtained using a W reinforcement phase content of 9 wt-%.