Chang-jun Lin

Optimal B-spline joint trajectory generation for collision-free movements of a manipulator under dynamic constraints

A method is proposed which describes the joint trajectories of a manipulator with B-spline curves, and which optimizes the values of these control points using the complex method under collision-free, full dynamic and kinematic constraints. This method utilizes the B-spline curves uniqueness, continuity, and local controllability to the control points, and incorporates the complex method which does not require evaluation of the gradient in the optimization. This method has the following advantages: (1) It is applicable to manipulators with arbitrary degrees of freedom; (2) It achieves the generation of the trajectory which takes the priority of specified constraints into consideration; (3) Weighting factors of the performance indices corresponding to the constraints are automatically computed. The method has been applied to the collision-free trajectory generation problems of a manipulator with three degrees of freedom and the results show its effectiveness.

Improvement of trajectory tracking for industrial robot arms by learning control with B-spline

This paper describes that a learning control algorithm with B-spline is effective to improve the trajectory tracking accuracy of an industrial robot and shows the results of simulation and experiment. The learning control method consists of two processes: Global Learning (GL) and Local Learning (LL). GL estimates the dynamics of a robot control system and obtains a learning gain matrix used in LL. LL decreases the tracking errors by iterative trial movements and acquires satisfactory tracking accuracy. The learning algorithm needs only measuring of position errors from a desired trajectory and does not require any derivatives of them. As the input trajectories after the convergence of learning are expressed by B-spline curves, they are easily memorized as input patterns corresponding to specified works.

Generation and optimality of trajectory described by B-spline

This paper discusses about the generation and optimality of the trajectory described by B-spline. In the trajectory generation values of B-spline control points are optimized by the complex method. The algorithm has following advantages: 1) it only needs computation of a performance index for the optimization but requires no computation of the gradient; 2) it is applicable to the problem of an arbitrary performance index to evaluate trajectories; 3) it can generate trajectories with continuous time derivative curves; and 4) it needs less memory to store the generated trajectories. For checking the optimality of the trajectories, it is applied to four types of trajectory generation: a manipulator trajectory generation, a solution of ordinary differential equation, a minimal time control problem, and a movement curve generation such as a cam curve one.

Control of mechatronic systems by learning actuator reference trajectories described by B-spline curves

Two algorithms are proposed for learning actuator reference trajectories to control mechatronic systems. The first algorithm uses the nominal dynamics and specified trajectories of the controlled systems. The algorithm is applicable to linear control systems. In the second algorithm the learning process does not require knowledge of the dynamics of the controlled system but only uses the performance index to evaluate motion of the system. This algorithm does not require specification of a trajectory. It is effective in the case that the system is nonlinear or difficult to identify. Two algorithms are obtained and applied to two systems: one involving trajectory tracking control for a one-link flexible arm and the other for learning the swing trajectory of an inverted pendulum.

A Practical Approach to Estimating Corner Errors in Contour Cutting with Machining Center

This paper proposes a practical approach to estimating the corner errors in contour cutting with a machining center. In this approach, only a few simple and easy trajectory measurements to linear feed motion of machining center are required and then the value of each necessary parameter is decided through a simple operation to the measured data. The comparison results of the estimated corner errors with the measured ones sufficiently demonstrate the effectiveness of the proposed approach.

A Simple and Convenient Sensor for Measuring Gasoline Engine Speed and Its Application in Flight Control of a Portable Unmanned Helicopter

In this paper, based on a very simple physical principle, a simple and convenient speed sensor for gasoline engine used in a portable unmanned helicopter (PUH) is developed. The sensor has several favorable features appropriate for a PUH control, i.e. small, light, taking little space, sufficient accurate and handling easy in control operation, especially, easy and low-cost in produce. Moreover, the same principle and structure is also applicable to a general gasoline engine. The experimental results with an actual PUH have sufficiently demonstrated the effectiveness and practicability of the sensor for the application of PUH control.

Selection of B-Spline Degree on Optimal Design of Mechanism

The degree is an important parameter for B-spline. In this paper, as one example of optimal design in mechanism, the optimal design of the cam curve to control the residual vibration of the follower output for an indexing cam mechanism is taken and the effect of the degree of the B-spline to describe the cam curve on the optimization performance is discussed by obtained results.

Measurement Errors of Coordinate Measuring Machine Produced by Touch Trigger Probe System

In this paper, the authors discuss the influence of touch trigger probe system on CMM measurement performance based on measurement experiment results. A ring gage and a plug gage finished in high accuracy are employed as test pieces and the measurements performed under the conditions of combining different extension bar and approaching speed. Two main types of errors, periodic component and high frequency undulation, are verified. Introduction of the extension bar may significantly aggravate the accuracy and reliability, especially, associated with a comparatively large approaching speed. In addition, from the discussions on the generation mechanism of the periodic error and high-frequency undulation, some worthwhile references to engineering applications are also derived.

A sensing device for gasoline engine speed of a miniature Portable Unmanned Helicopter

This paper presents a sensing device for gasoline engine speed used in a miniature Portable Unmanned Helicopter (PUH). The sensing device has several favourable features appropriate for PUH control, i.e., small, light, accurate and easy to handle in the control operation, especially, easy and low-cost for manufacturing. Moreover, it is also applicable to general gasoline engines. Experimental results with a miniature PUH have demonstrated the effectiveness and practicability of the sensing device for the application in PUH control. The novel method has been submitted for Patent in Japan.

A feedback control gain tuning for mechatronic systems by iterative trials

A feedback gain tuning method is proposed to control mechatronic systems which have the characteristic applicable to iterative trial movements. The tuning algorithm is composed of an optimization procedure based on the complex method and has the following features: (1) it does not require any dynamic model of controlled systems; (2) it tunes the feedback gain under an arbitrary performance index and is applicable to both linear and nonlinear control laws; (3) the algorithm is concise and has a few adjusting parameters; and (4) the tuning process proceeds well and the on-site tuning for actual systems is possible. It is also confirmed by the experiments using both simulations and actual systems that the proposed tuning method is effective to the stabilization control of an inverted pendulum.