Showing papers in "Jsme International Journal Series C-mechanical Systems Machine Elements and Manufacturing in 1997"

Adaptive Terminal Sliding Mode Tracking Control for Rigid Robotic Manipulators with Uncertain Dynamics.

Abstract: A robust adaptive terminal sliding mode tracking control is proposed for rigid robotic manipulators. First, it is shown that, when a rigid robotic manipulator is treated as a partially known system, the system uncertainty is not only related to the model properties but also to the structure of the controllers. It is also proved that, if the control input vector does not contain the acceleration signals, the system uncertainty is upper bounded by a positive function of the position and velocity measurements. The property is very useful for the design of robust and adaptive controllers where only position and velocity measurements are available. Second, an MIMO terminal sliding mode is defined for the error dynamics of the robot control system, and an adaptive mechanism is introduced to estimate the upper bounds of system uncertainty in the Lyapunov sense. The estimates are then used as controller parameters so that the effects of uncertain dynamics can be eliminated and a finite time error convergence can be guaranteed. A simulation is given in support of the proposed control scheme.

Simulation of Trabecular Surface Remodeling based on Local Stress Nonuniformity.

Abstract: In this study, to investigate mechanical remodeling of cancellous bone from the viewpoint of trabecular surface remodeling due to trabecular level mechanical stimuli, a rate equation for trabecular surface remodeling is proposed based on the uniform stress hypothesis, which suggests that nonuniformity in the local stress distribution on the trabecular surface is the driving force for remodeling. A proposed local rate equation for trabecular surface remodeling is applied to a computational simulation of morphological changes, in which the trabeculae are modeled as an assemblage of two-dimensional boxel elements and their morphological changes are simulated by removal / addition of the elements from / to the trabecular surface. The basic features of the proposed rate equation and simulation method are investigated through remodeling simulations applied to the basic trabecular-level structure, cancellous-bone-level structure and the proximal femur. In all cases, the trabecular orientation, thickness and connectivity are adapted to the mechanical environment, which demonstrates the capability of the proposed rate equation for computational prediction of the adaptation phenomenon and supports the hypothesis regarding the optimality of trabecular architecture as a mechanical load bearing structure.

On-Machine Profile Measurement of Machined Surface Using the Combined Three-Point Method

Abstract: The combined 3-point method, which combines the generalized 3-point method with the sequential 3-point method, is described in the present paper. The combined 3-point method can not only measure profiles that include high-frequency components whose spatial wavelengths are shorter than the probe distance, but also cancel the influence of the z-directional error and the pitching error in the scanning motion. In the combined 3-point method, some data points from a profile evaluated by the generalized 3-point method are chosen as reference points of the standard area and are used to determine the relative heights among the data groups of the sequential 3-point method. An automatic selection method was used to select the standard area correctly and quickly. Theoretical analyses and computer simulations were performed to confirm the effectiveness of the combined 3-point method. Experimental profile measurements were also carried out using three capacitance-type displacement probes.

Development of Three-Diemnsional Whole-Body Musculoskeletal Model for Various Motion Analyses

Abstract: A simulation model for biomechanical analysis was developed in order to calculate the internal loads, such as muscular tension and energy consumption, from measured kinesiological data for various kinds of motion. In this model, the human body is divided into a maximum of nineteen rigid segments connected to each other with ball joints. A maximum of 156 skeletal muscles throughout the body are modeled as tensile force generators which include physiological elements that consume mechanical energy. The component ratio among muscle fiber types, number of body segments and number of degrees of jointfreedom can be changed easily, and according to the alteration of the segment number, the musculoskeletal system is changed automatically. This flexibility is of benefit in application of the method to various motion analyses. Three-dimensional bipedal walking was analyzed using a simplified model, and rowing motions were analyzed using the whole-body model.

A Thermal-Expansion-Type Microactuator with Paraffin as the Expansive Material (Basic Performance of a Prototype Linear Actuator)

Abstract: Our aim is to develop a microactuator for use in endoscopic-surgery. The purpose of this study was to construct cylinder-piston-type microactuators actuated by thermal expansion of paraffin. We use paraffin as the material for expansion because paraffin has a large coefficient of expansion in the temperature range of 35 to 45 degrees centigrade. For smooth actuation of the piston, we must prevent the paraffin from sticking to the inside surface of the cylinder. Thus, the paraffin is enclosed in a silastic tube. The cavity between the cylinder and the tube is filled with silicone oil for lubrication and prevention of expansion loss. The outer diameter of the actuator is 2.5 mm and its length is 130 mm. The actuator can generate a stroke of 8mm against a load of 1 kg.

Development of Spatial In-Parallel Actuated Manipulators with Six Degrees of Freedom with High Motion Transmissibility.

Abstract: The dimensional synthesis of the mechanism of an in-parallel actuated manipulator should take into account high motion transmissibility and avoidance of the area surrounding singular points as well as the singular points in the prescribed working space. In this paper we propose a new method based on the Monte-Carlo technique to obtain the kinematic constants which assure high motion transmissibility. This method has been applied to dimensional synthesis of a 6-RSS type spatial in-parallel actuated manipulator with six degrees of freedom. The effectiveness of the proposed method has also been investigated by comparison of the results to those obtained by the conventional method. These results have been used to develop a manipulator driven by direct drive motors. The position repeatability has been experimentally investigated and the result reveals that the manipulator can be used to realize precise positioning superior to those of conventional industrial robots.

Properties of Vibration with Fractional Derivative Damping of Order 1/2.

Abstract: The general properties of a harmonic oscillation with damping proportional to the fractional time derivative of the displacement of order 1/2 is studied. It is shown that vibration decays when the damping coefficient is positive, implying that the model is thermodynamically valid. The center of the oscillation is a curve that approaches the time axis algebraically, so that after the oscillation damps out, there is a long trailing tail. There is no critical value of the damping coefficient that distinguishes the pattern of damping. For a negative damping coefficient, oscillation grows exponentially. An equivalent oscillator model with ordinary damping may be constructed for small damping, which shows that fractional damping acts partly as a supplementary spring, reflecting the recoil effect of a viscoelastic material.

Monitoring of Tool Wear States in Turning Based on Wavelet Analysis

Abstract: In this paper, a novel signal processing tool, the wavelet transform, was applied to monitor the flank wear states in turning. The wavelet transforms were implemented by FWT(fast wavelet transform)based on a QMF(quadrature mirror filter). The expansion coefficients d(j, k)with time-frequency feature obtained by FWT were used as recognition parameters of the flank wear states. The dynamic characteristics of the cutting force signals were analyzed separately using the wavelet transform and the Fourier transform. The abilities of these two transforms for analyzing and recognizing the flank wear states were compared. The experimental and analytical results show that when monitoring the flank wear states during turning, the wavelet analysis is more sensitive, more reliable and faster than the Fourier analysis.

Active and regenerative control of an electrodynamic-type suspension

Abstract: Active vibration dampers and isolators are capable of reducing vibration, and the results are remarkable and can be achieved adaptively. However, they require a large amount of energy to control the vibration. Since structural vibration has motional energy, a question arises as to how we can utilize this energy rather than just simply suppressing it. In this paper an energy regenerative type suspension is presented which utilized an electrodynamic actuator to regenerate electric power during the high-speed motion of the actuator. At low-speed motion, an active control algorithm is applied to the same actuator to provide good damping performance. In order to reduce energy loss in the control amplifier, active relay control is applied instead of linear control. The system is first simulated on a computer and followed by a simple experiment similar to a suspension system. The results are very encouraging and show that the system performed better than a passive suspension system and can regenerate vibration energy.

Review of Gear Efficiency Equation and Force Treatment

Abstract: With the present interest in energy saving, the improvement of gear efficiency is being looked at again. In this paper, differences between Buckingham's and Merritt's gear efficiency equations are described. These equations are of the same calculation form, but the manner in which they are used differs. The equations are valid under the assumption that input energy is calculated as the product of the normal force and displacement along the line of action. The author clarifies that an incorrect manner of calculating input power in the meshing gear may lead to trouble, and that Buckingham's and Merritt's equations are approximations. Moreover, in this paper a problem derived from the treatment of pitch point force is described. From the results of this study, it is concluded that the use of a tangential force of the pitch circle leads to an incorrect theory. The author deals with the locking phenomenon of the planetary gear mechanism as an example.

Development of Robust Active Rear Steering Control for Automobile

Abstract: A new concept for a robust active rear steering(ARS)system is presented. The system exhibits good control performance even if the vehicle parameters and / or road surface conditions are changed. This system makes the vehicle follow the desired dynamic model by state feedback of both yaw rate and side slip angle. For utilization of a noisy yaw rate sensor and maintenance of high robust control performance, a controller with frequency-dependent gain characteristics was designed by μ synthesis. For estimatation of the side slip angle using a noisy sensor, a new time-variant observer employing a frequency filter was introduced. The results of the simulation and the experimental tests prove the great effect of the new ARS system.

Sensory Evaluation of Grip Using Cylindrical Objects.

Abstract: In order to clarify the grasping mechanism of tools and machine handles, sensory tests to evaluate the optimum grasping diameter have been performed on forty-three people from age seven to fifty-three. It was confirmed that the sensory evaluation of the optimum grasping diameter was difficult for children under age ten due to insufficient growth of skeletal structure. The optimum grasping diameter was evaluated for persons above age ten. The optimum grasping diameter depended on the hand size, and the dependency was marked for children under eleven. In the case of adults, the optimum grasping diameter depended on the dimensions concerned with the length of the hand but only depended slightly on the hand breadth or fist. The optimum grasping diameters evaluated for males were 30∼40mm, which were about 10% larger than those evaluated for females. As a result of investigating above data, it was found that the tube could be grasped well by a human hand if all fingertips and the entire palm area contact it.

Polygonal wear of automobile tire

Abstract: This study investigates, experimentally and analytically, the polygonal wear of truck / bus and car tire and elucidates the generation mechanism of polygonal wear caused by the first natural vibration mode of the tire in the vertical direction. In the analysis, the phenomenon is modeled as a time delay system accompanied by wear in which the amount of wear of the tire is fed back as forced displacement in the vertical direction after the time period of tire rotation. The progress of the polygonal wear of the tire is very slow and is caused by unstable vibration in the steady-state wear process generated in the limited regions where the products of polygonal numbers and the rotational speed of the tire are less than the natural frequencies of the tire system. The tire is deformed almost to the shape of a regular polygonal when polygonal wear occurs. Good agreement between experimental and analytical results concerning the occurrence of polygonal wear of the tire was confirmed.

Multivariable Identification of Active Magnetic Bearing Systems

Abstract: Magnetic bearing systems are unstable MIMO1) plants. In addition, there may be poorly damped resonances of the levitated rotor. Advanced control is a crucial issue. System identification is therefore an important prerequisite for fast and reliable commissioning. Reported algorithms have difficulties to estimate the real unstable poles in magnetic bearing systems. Thus, a novel identification algorithm has been developed. Experimental results are included.

Fuzzy PWM control of the positions of a pneumatic robot cylinder using high speed solenoid valve

Abstract: In the study, instead of using expensive servo valves, three inexpensive high-speed solenoid valves were adopted and a fuzzy PWM controller was designed to control the linear and rotational positions of a pneumatic robot cylinder. The modified differential PWM method is proposed to eliminate the dead zone and to improve the nonlinear characteristics between the pressure difference of the cylinder and the duty ratio of the PWM control signal. The experimental results have shown that the servo pneumatic system with the proposed fuzzy PWM controller exhibits good performance.

Inverse Dynamics Compensation Method for PWS Mobile Manipulators

Abstract: A robot system composed of a mobile robot and a manipulator is called a "mobile manipulator". In this paper a calculation method of inverse dynamics compensation for a power-wheeled-steering(PWS)mobile manipulator is proposed. Newton-Euler method is used for the compensation calculation. A mobile manipulator dirrers from a floor-fixed manipulator in that it moves according to non-holonomic constraints. As the constraints integrate velocity and angular velocity errors of the mobile manipulator on a floor, the errors influence the hand position and orientation of the mounted manipulator. The integrated errors do not disappear even after the dynamical vibration of the mobile manipulator is settled. Therefore, to reduce the integrated errors, the velocity errors of the mobile manipulator should be reduced. We propose a calculation method, and the effects of the method are confirmed by simulation experiments.

Float Characteristics of Squeeze-Film Gas Bearing with Elastic Hinges for Linear Motion Guide.

Abstract: In this paper we describe the float characteristics of a new type of squeeze-film gas bearing which can be used to realize non-contact linear-motion guide systems which do not require supply of pressurized air. Piezoelectric actuators and elastic hinges are used to induce vibration of the bearing and generate squeeze-film pressure under the bearing. In a theoretical analysis, a simple dynamic model of the bearing structure is presented. The influences of the displacement and vibrational frequency of the piezoelectric atcuators on the float characteristics are investigated theoretically and experimentally. Furthermore, the load capacity at a vibrational frequency of 2400 Hz and the float characteristics at the resonance frequency of the bearing are measured. It was found that the bearing can be used to realize a non-contact linear motion guide and that the dynamic model presented in this paper can be used for accurate prediction of the float characteristics of the bearing.

Magnetic Bearings. State of the Art of Magnetic Bearings. (Overview of Magnetic Bearing Research and Applications).

Abstract: Magnetic bearings levitate, suspend and guide rotors by magnetic forces without physical contact. The non-contact support offers many advantages and opportunities for a wide variety of applications. Since the First International Symposium on Magnetic Bearings was held in Zurich in 1988, this field of research has expanded, and competition in research and development has been very keen. This review presents the recent trends in applications, control methodologies, sensorless controls, bearingless motors, unbalance control, problems of flexible rotors, eddy current properties and power amplifiers.

Running Test on Current Collector with Contact Force Controller for High-Speed Railways

Abstract: To reduce noise caused by current collectors on high-speed railways, a wing-Shaped low-noise current collector has been developed. This collector head is directly supported by a composite insulator. However, it becomes difficult to maintain the predetermined contact force of the contact strip against the trolley wire. Therefore, the vertical height of those apparatus should be controlled actively. The upper part of the composite insulator is under high voltage. When using sensors only under the insulator, it is difficult to distinguish wire disturbance from lift disturbance. In this study, the difficulty is solved by using H∞ controller to estimate those disturbances in each frequency range. In traveling experiments using full-size prototype equipment on the running vehicle, it was confirmed that the contact force variation due to lift of 68 N at the speed of 112km / h was reduced by about 33% compared with active control without lift compensation, and the wire push-up variation was reduced by about 67%.

Robust Vibration Control of a Cantilever Beam Using Self-Sensign Actuator

Abstract: The self-sensing actuator is a new concept for intelligent materials, where a single piezoelectric element simultaneously functions as both a sensor and an actuator. This concept should be advantageous in many aspects of control, especially for vibration control of flexible structures. The key component of this device is an electric bridge circuit that includes a piezoelement. This circuit could provide significant information about strain in the element if it were wellbalanced. Our aim is to use μ-synthesis to design a controller which guarantees that the performance of a self-sensing actuator is robust against perturbations in the bridge balance and to confirm the advantages of this technique from the viewpoint of control. Experimental results show that the self-sensing actuator driven by the designed controller exhibits excellent performance in suppressing the vibration of a cantilever and is robust compared to the conventional control scheme.

Constant Speed Control of the Quick Return Mechanism Driven by a DC Motor.

Abstract: For the dynamic analysis, Hamilton's principle and Lagrange multiplier method are applied to formulate the equations of the motion of a quick return mechanism driven by a DC motor. The coordinate partitioning theorem is applied here to provide a theoretical reduction of differential-algebraic equations to differential equation form. In this work, we are concerned with the analysis and design a modified proportional-integral-derivative(PID)controller which was based on the principles of conventional PID controller to keep the driving crank with a constant angular velocity. Results of numerical simulations show that the angular velocity fluctuation can be reduced substantially and this modified PID controller also can give reasonably good results whatever it have or not considered cutting force in the system.

Lubricating Ability of Langmuir-Blodgett Films as Boundary Lubricating Films on Articular Surfaces

Abstract: Frictional behavior in sliding pairs of pig articular cartilage and glass plate has been studied to elucidate the tribological role of constituents in a synovial fluid and a surface layer of the articular cartilage. Pig synovial fluid and water solution of hyaluronic acid were used as lubricants. The synovial fluid had a significantly superior lubricating ability to a sodium hyaluronate solution of equivalent viscosity under physiologically high load condition. The superiority of the synovial fluid seems to be responsible for the boundary lubricating ability of constituents other than hyaluronic acid. Langmuir-Blodgett films of phospholipid (Lα-dipalmitoyl phosphatidylcholine, Lα-DPPC) on the glass plate maintained low and stable friction, depending on the number of film layers. In conditions of mixed films containing γ-globulin and Lα-DPPC, the frictional behavior was improved by increasing the quantity of γ-globulin. A model of the boundary lubricating mechanism is proposed in which the effective adsorbed film is composed of proteins, phospholipids and other conjugated constituents on the articular surfaces, and controlled by hydrophobic groups in those amphiphiles.

ETS-VI On-Orbit System Identification Experiments.

Abstract: System identification and attitude control experiments have been performed as part of a series of bus experiments on the Engineering Test Satellite-VI, which was launched by an H-II rocket in August 1994. The aims of the experiments were to establish a pre-launch system dynamics modeling method, to evaluate typical on-orbit modal parameter identification methods and to develop robust and precise attitude controller design technology for future large flexible spacecraft and large space structures. In the on-orbit identification experiments, the central body of the satellite was excited by gas jet thrusters and the measured attitude and paddle accelerometer signals were downlinked by telemetry. In this paper, the identified parameters are compared with those of the pre-launch modeling and the accuracy of the pre-launch model is evaluated.

Design System of Superelastic Hinges and Its Application to Micromanipulators

Abstract: In order to develop a micromanipulator system for microbonding by adhesive, the characteristics of superelastic hinges made of superelastic materials, for example, shape memory alloy, have been analyzed and represented in the form of charts which enable rational design of micromanipulators. Making use of the characteristic charts, shapes and sizes of hinges can be considered in the determination of the kinematic parameters of a pantograph mechanism with superelastic hinges. The effective performance of the design system is demonstrated using an example of a manipulator for microbonding by adhesive.

Self-localization for an electric wheelchair

Abstract: This paper presents an autonomous wheelchair system with the capability of self-localization. In our system, the ceiling lights are chosen as landmarks to realize the self-localization and auto-navigation of the wheelchair. An approach to landmark recognition is described, and a technique of self-localization for the wheelchair is proposed. Subsequently, the path planning for navigation is discussed. Finally, the total system for our wheelchair is introduced, and a navigation experiment is described. Experimental results indicate the effectiveness of our system.

Analysis of Impact Phenomena in a Tennis Ball-Racket System : Effects of Frame Vibrations and Optimum Rocket Design

Abstract: The performance of a tennis racket in terms of the coefficient of restitution (COR) is closely related to impact phenomena. This paper investigates the effects of frame vibrations on the coefficient of restitution and the contact time during impact of a ball/ string system and a simulated frame model, using FEM simulation and modal analysis. The results show that the COR is mainly affected by a rigid motion and a bending vibration with two nodes of racket frame. In addition, the COR increases with an increase of frame rigidity, but then saturates at a certain rigidity depending on the impact velocity. Furthermore, the COR increases as the impact point approaches the center of rotation and the node of racket frame vibration.

Kinematic and Sensitivity Analyses of a New Type Toggle Mechanism

Abstract: This paper is devoted to the kinematic and sensitivity analyses of a new designed toggle mechanisms which is the combination of two slider-crank mechanism The analytic analysis is developed for obtaining the general equations of position, velocity, and acceleration for each link Three common types of motion including constant acceleration, simple harmonic and cycloidal are considered as the inputs while the corresponding outputs between two toggle positions are studied By using geometric relationships and trigonometry, the various results of kinematic and sensitivity analyses are presented and compared between the four-point type and five-point type toggle mechanism

Active Vibration Control by Means of LMI-Based Mixed H2 / H∞ State Feedback Control

Abstract: In this paper, mixed H2 / H∞ control is studied using the linear matrix inequality approach(LMI). In many linear control problems, the design constraints can be reformulated in terms of LMI. In general, in H∞ control good frequency response performance is maintained but transient response of control system may not be guaranteed. Here, we have formulated H∞ and H2 control separately by means of LMI, and combined both objectives as a mixed control problem. We applied mixed H2 / H∞ control to an active vibration control problem and obtained reasonable results in frequency and time domains. The design approach described here is based on a numerical optimization technique which requires use of efficient convex optimization software.