Showing papers in "Mechatronics in 2001"
TL;DR: In this article, the experimental comparison among four model-based control algorithms on a direct-drive robotic arm is presented, including Coulomb and viscous friction compensation as well as cancellation of gravitational torques.
Abstract: This paper describes the experimental comparison among four model-based control algorithms on a direct-drive robotic arm. We present experimental results of the following controllers: Computed-Torque control, PD+ control, PD control with computed feedforward and PD control. All controllers include Coulomb and viscous friction compensation as well as cancellation of gravitational torques. They are tested under common trajectory specification and performance index.
117 citations
TL;DR: In this article, the design and development of a force-torque sensor based on the Stewart platform structure is described, and the optimal synthesis of the sensor structure is performed with the objective of achieving well-conditioned transformation between the input and output forces.
Abstract: This paper details the design and development of a force–torque sensor based on the Stewart platform structure. The optimal synthesis of the sensor structure is performed with the objective of achieving well-conditioned transformation between the input and output forces. The influence of size of platform on sensitivity and the load bearing capacity are discussed in the light of capabilities of available sensing elements. Thus, the design is obtained by satisfying the dual objective of isotropy and sensitivity of the force–torque sensor. Maximization of signal to noise ratio (S/N ratio) is considered at various stages in arriving at various component shapes and dimensions. The above design has been implemented in the development of a compact force–torque sensor.
104 citations
TL;DR: In this paper, a hybrid actuator scheme is proposed to actively control the end-point position of a two-link flexible manipulator, which consists of four actuators; two servo-motors at the hubs and two piezoceramics attached to the surfaces of the flexible links.
Abstract: This paper presents a hybrid actuator scheme to actively control the end-point position of a two-link flexible manipulator. A highly nonlinear system model including inertial effect is established using Lagrange's equation associated with assumed mode method. Control scheme consists of four actuators; two servo-motors at the hubs and two piezoceramics attached to the surfaces of the flexible links. Two sliding hyperplanes which have time-varying parameters are designed for two servo-motors. The surface gradients of the hyperplanes are determined by pole assignment technique to guarantee the stability on the hyperplanes themselves. The sliding mode controllers corresponding to the hyperplanes are then synthesized on the basis of an equivalent rigid-link dynamics to the proposed flexible manipulator. During the motion, undesirable oscillations caused by the torques based on the rigid-link dynamics are actively suppressed by applying feedback control voltages to the piezoceramic actuators. Consequently, the desired end-point motion is achieved. In order to demonstrate the effectiveness of the proposed methodology both regulating and tracking control responses are evaluated through experimental realization.
100 citations
TL;DR: In this paper, the performance characteristics of a semi-active ER (electro-rheological) suspension system were evaluated through the field test of a passenger car, and four ER shock absorbers were designed and manufactured for both front and rear parts, and their field-dependent damping properties were investigated.
Abstract: Performance characteristics of a semi-active ER (electro-rheological) suspension system are evaluated through the field test of a passenger car. Four ER shock absorbers are designed and manufactured for both front and rear parts, and their field-dependent damping properties are investigated. Subsequently, four independent skyhook controllers associated with ER shock absorbers are formulated by considering the vertical motions of the body and wheel of the car to be tested. Both ride comfort and steering stability of the car are evaluated via the field test showing bump and squat test responses.
92 citations
TL;DR: In this article, the authors proposed a path-tracking algorithm to compensate for path deviation due to torque limits, which uses a disturbance observer with an additional saturation element at each joint of n degrees of freedom (DOF) manipulator.
Abstract: This paper proposes a path-tracking algorithm to compensate for path deviation due to torque limits. The algorithm uses a disturbance observer with an additional saturation element at each joint of n degrees of freedom (DOF) manipulator to obtain a simple equivalent robot dynamic (SERD) model. This model is represented as an n independent double integrator system and is designed to ensure stability under input saturation. For an arbitrary trajectory generated for a given path in Cartesian space whenever any of the actuators is saturated, the desired acceleration of the nominal trajectory in Cartesian space is modified on-line by using SERD. An integral action with respect to the difference between the nominal and modified trajectories is utilized in the nonsaturated region of actuators to reduce the path error. To verify the effectiveness of the proposed algorithms, real experiments were performed for a two DOF SCARA-type direct-drive arm.
87 citations
TL;DR: The paper describes design, construction and experimental testing of an active gait orthosis intended to assist locomotion in paraplegic subjects and results consisting of graphs and photographic images are presented.
Abstract: The paper describes design, construction and experimental testing of an active gait orthosis intended to assist locomotion in paraplegic subjects. Design specifications were formulated on the basis of an analysis of the context in which the device will be used. Different joint activation solutions were then proposed and examined. Considerable care was devoted to defining the logic and control system and to implementing the electro-pneumatic circuit, given that the system must be worn by a disabled subject who has no sensory perception in the lower limbs. Experimental tests, which made it possible to determine system performance at each step of development, were carried out with no user, then with a healthy user and finally with a paraplegic user. Experimental results consisting of graphs and photographic images are presented and discussed.
79 citations
TL;DR: In this article, a robust force tracking control of a flexible gripper using shape memory alloy (SMA) actuators is presented, and the H ∞ -controller is synthesized by treating the uncertain parameter as coprime factor.
Abstract: This paper presents a robust force tracking control of a flexible gripper using shape memory alloy (SMA) actuators. The governing equation of a partial differential form for the flexible gripper is derived by employing Hamilton’s principle, and a state-space control model is obtained by retaining a finite number of vibration modes. In the formulation of the control model, time constant of the SMA actuator is treated as uncertain parameter. This is adopted due to the fact that the SMA actuator has different time constant at the heating and cooling stage, respectively. The H ∞ -controller is then synthesized by treating the uncertain parameter as coprime factor. The specifications of stability margin and steady state error to achieve robust performance are imposed, and the first-order reference model is augmented to avoid excessive overshoot. After analyzing the robust stability of the system using the singular value plot, the controller is experimentally realized and force tracking control responses for step and sinusoidal force trajectories are presented in time domain to demonstrate the effectiveness of the proposed methodology.
78 citations
TL;DR: In this article, a method of automated level-digging control is proposed, where the boom tip height is controlled so that the bucket tooth tip can be moved horizontally, thereby increasing the working efficiency level.
Abstract: The hydraulic excavator is used at a wide variety of sites. Its diversity and convenient operating nature make it popular. Among the different types of work performed by hydraulic excavators, level digging work accounts for a large percentage. When digging or finishing ground surfaces level using the backhoe front attachment, the boom tip height must be controlled so that the bucket tooth tip can be moved horizontally. This paper describes a method of automated level digging control we wish to propose. By using this control system, depth controlled digging can be achieved in the same way as usual manual lever operation while minimizing repetitive depth confirmation work, thereby raising the working efficiency level.
76 citations
TL;DR: The results from the experiments show that the proposed hybrid of fuzzy and PID control gives the most satisfied settling time and steady-state error.
Abstract: In a pneumatic system, normally, the piston can stop at only two terminal endpoints. In order to extend the capabilities of the system, this research is conducted to develop a kinematics control-based pneumatic system. Both position and velocity of the pneumatic piston are controlled in such a way that the controlled piston is able to move with the specified velocity to the target position. A hybrid of fuzzy and proportional-plus-integral-plus-derivative (PID) control algorithm is proposed in this paper as the solution. The control algorithm is separated into two parts: fuzzy control and PID control. The fuzzy controller is used to control the piston when the piston locates far away from the target position whereas the PID controller is applied when the piston is near the desired position. The development starts with designing of a position sensor to detect position information of the piston. The sensor-manipulating circuit consisting of potentiometer, inverting amplifier, summing amplifier, low-pass filter and analog-to-digital converter is then designed and realized. Next, the proposed hybrid of fuzzy and PID control is implemented and programmed on the microprocessor. In order to test performance of the system, settling time and steady-state error of five control algorithms – proportional (P) control, proportional-plus-integral (PI) control, proportional-plus-derivative (PD) control, PID control, and hybrid of fuzzy and PID control – are investigated. The results from the experiments show that the proposed hybrid of fuzzy and PID control gives the most satisfied settling time and steady-state error.
75 citations
TL;DR: The method has been used to guide a mechanical hoe in winter wheat with an RMS positional error of 15.6 mm at a speed of 1.6 ms −1 , despite the presence of complex shadows cast by the tractor in the imaged area.
Abstract: A method of locating crop rows in image sequences is described. Unlike several previously reported algorithms, the method does not rely upon the segmentation of plant material from the background on the basis of absolute brightness or colour. Rather, the periodic amplitude variation due to parallel crop rows is exploited. Given the geometry of the camera arrangement and the crop row spacing, a filter is derived which allows the crop rows to be extracted whilst attenuating the effects of partial shadowing and spurious features such as weeds. The position and orientation of the rows are tracked using an extended Kalman filter. The method has been used to guide a mechanical hoe in winter wheat with an RMS positional error of 15.6 mm at a speed of 1.6 ms −1 , despite the presence of complex shadows cast by the tractor in the imaged area.
71 citations
TL;DR: In this paper, an adaptive control system based on a novel design of the boring bar containing an Electrorheological fluid, automatically adjusts the dynamics of the bar according to the information from the monitored sensor signal.
Abstract: For on-line chatter avoidance in boring, this paper presents an adaptive control system which, based on a novel design of the boring bar containing an Electrorheological (ER) fluid, automatically adjusts the dynamics of the bar according to the information from the monitored sensor signal. For detecting chatter rapidly and accurately, artificial neural networks are used to decontaminate the sensor signal and recognize the chatter omen. Once chatter is detected, a strength regulation strategy of the electric field applied to the ER fluid in the bar is used to suppress chatter. When a certain electric field is applied to the ER fluid in the bar it behaves as a viscoelastic spring with nonlinear vibration characteristics. Based on the nonlinear vibration characteristics of the ER fluid, the strength regulation strategy is to tune the electric field strength so that the dynamics of the bar is sensitive to the minute change of the vibration amplitude. Experiments show that chatter in boring can be avoided by using this control system.
TL;DR: In this article, a method to control a two-fingers gripper for safe grasping of fragile and delicate objects like glass, fruits or vegetables is presented, where the controller receives the object velocity and acceleration and the detection of incipient slippage and adjusts the fingers motion.
Abstract: This paper presents a method to control a two-fingers gripper for safe grasping of fragile and delicate objects like glass, fruits or vegetables. The proposed control algorithm adjusts the motion of the fingers of a gripper using tactile feedback, so that an object is grasped with the minimal required force without the measurement of this force. The rules set of the control law is derived empirically by investigation of the human finger skills. The formulation of these rules and the inference mechanism are based on fuzzy logic. The controller receives the object velocity and acceleration and the detection of incipient slippage and adjusts the fingers motion. The main advantage of this method is that the designed controller is quite robust because knowledge concerning the size, the weight or the surface texture of the grasped object is not required. The object is stably grasped by applying a relatively low grasping force. Simulated experiments are presented to demonstrate the efficiency of the introduced fuzzy controller of robot grippers, while its performance is compared with a PID controller.
TL;DR: In this article, an adaptive energy-based robust control is presented for both closed-loop stability and automatic tuning of the gains of the additional control terms for desired performance, and simulation results are provided to show the effectiveness of the presented approach.
Abstract: Energy-based robust control strategy was proposed in [12] to improve the control performance of the traditional joint PD control by introducing additional control efforts through the evaluation of vibration related variables. Although the energy-based robust controller always guarantees closed-loop stability, it is not easy to find suitable gains of the terms for a satisfactory control performance. In this paper, adaptive energy-based robust control is presented for both closed-loop stability and automatic tuning of the gains of the additional control terms for desired performance. Simulation results are provided to show the effectiveness of the presented approach.
TL;DR: In this article, the authors presented a methodology for the design of optimal kinematical characteristics of Stewart platform using genetic algorithms (GAs), where the minimum of condition numbers of Jacobian matrix in the whole trajectory tracing workspace is used as the objective function, and the constrained optimal design problem is transformed to unrestrained optimal one which is suitable to GAs by penalizing strategy.
Abstract: This paper presents a methodology for the design of optimal kinematical characteristics of Stewart platform using genetic algorithms (GAs). The optimal kinematics index which expressed by Jacobian matrix of Stewart platform is first deduced, and then the minimum of condition numbers of Jacobian matrix in the whole trajectory tracing workspace is used as the objective function. The constrained optimal design problem is transformed to unrestrained optimal one which is suitable to GAs by penalizing strategy, and the corresponding real-encoding scheme is used. This genetic methodology for optimal kinematical Stewart platform is illustrated by applying to design the fine tuning Stewart platform for large spherical radio telescope, and its validity is verified with the kinematic accuracy comparison of genetic-designed fine tuning platform with that of conventional Quasi-Newton optimal method.
TL;DR: A device to augment an existing force feedback haptic display with a vibrotactile display, thus providing a means of conveying low amplitude, high frequency spatial information of object surface properties.
Abstract: Current force feedback, haptic interface devices are generally limited to the display of low frequency, high amplitude spatial data. A typical device consists of a low impedance framework of one or more degrees-of-freedom (dof), allowing a user to explore a pre-defined workspace via an end effector such as a handle, thimble, probe or stylus. The movement of the device is then constrained using high gain positional feedback, thus reducing the apparent dof of the device and conveying the illusion of hard contact to the user. Such devices are, however, limited to a narrow bandwidth of frequencies, typically below 30 Hz, and are not well suited to the display of surface properties, such as object texture. This paper details a device to augment an existing force feedback haptic display with a vibrotactile display, thus providing a means of conveying low amplitude, high frequency spatial information of object surface properties.
TL;DR: In this paper, a five-bar finger with redundant actuation is designed and implemented, and the optimal sets of actuator locations and link lengths for cases of a minimum actuator, one-, two-, and three-redundant actuators are obtained by employing a composite design index which simultaneously considers several performance indices, such as workspace, isotropic index, and force transmission ratio.
Abstract: In order to develop a human hand mechanism, a five-bar finger with redundant actuation is designed and implemented. Each joint of the finger is driven by a compact actuator mechanism having an ultrasonic motor and a gear set with a potentiometer, and controlled by a VME bus-based control system. Optimal sets of actuator locations and link lengths for cases of a minimum actuator, one-, two-, and three-redundant actuators are obtained by employing a composite design index which simultaneously considers several performance indices, such as workspace, isotropic index, and force transmission ratio. According to the optimization result, several finger-configurations optimized for a special performance index are illustrated, and it is concluded that the case of one redundant actuator is the most effective in comparison to the cases of more redundant actuators, and that the case of two redundant actuators is the most effective in multi-fingered operation in which the force characteristic is relatively important, as compared to the kinematic isotropy and the workspace of the system.
TL;DR: In this article, a piezoactuator-driven optical pick-up for compact disc-read only memory (CD-ROM) drive is proposed to achieve fine motion control of objective lens.
Abstract: This paper proposes a piezoactuator-driven optical pick-up for compact disc-read only memory (CD-ROM) drive in order to achieve fine motion control of objective lens. The dynamic model of the proposed optical pick-up consisting of piezoceramic bimorph, wire suspension and objective lens is derived from Hamilton’s principle. A state-space control model is subsequently formulated by considering hysteresis behavior of the piezoactuator and frequency variation of the device as uncertainties. A sliding-mode controller, which is known to be robust to system uncertainties is designed for fine motion tracking control of the objective lens in vertical direction (focusing). The controller is then experimentally realized and position-tracking responses of the optical pick-up are presented in time domain. In addition, control durability is demonstrated by showing favorable tracking performance of a sinusoidal trajectory up to 8000 cycles of operation.
TL;DR: In this article, the authors describe the development and prototype testing of a platform for micropositioning having three legs made of piezo tubes, each of which has four outer electrodes and one common inner electrode on its walls.
Abstract: In this paper, we describe the development and prototype testing of a platform for micropositioning having three legs made of piezo tubes. Each piezo tube has four outer electrodes and one common inner electrode on its walls. By appropriate polarization of outer(s) electrode(s) with respect to the inner electrode, due to the inverse piezo effect, the tube wall will change its longitudinal dimension and the tube will bend in the corresponding direction. The platform motion is performed by successive slow bending and quick stretching of the tubes (i.e., legs). At this stage of development, the platform is connected by five wires to a power supply and a PC. The range of platform motion is limited only by the length of the wires connecting it to the power source. Electronic circuits for generating appropriate voltage signals are designed to be as simple as possible. This enabled the complete electronics and microcontroller for motion control to be placed onboard. The microcontroller is capable of realizing all operations needed for the motion execution and the communication with PC (containing the information about motion direction and step amplitude) can be done using a standard RS-232 interface. It was experimentally verified that, though being of a simple design, the platform allows a positioning accuracy which is below 0.2 μm . Even more accurate positioning (below 0.1 μm ) can be achieved in the “only bending” mode by simultaneous bending of all legs in a desired direction and without executing the legs' stretching. The platform capability to accomplish controlled complex motion using different motion velocities was demonstrated. Using a joystick, translation and rotation are easily achievable and the motion can be controlled in real time. Platform loading capacity allows some additional devices like a gripper, or any another device for a particular application to be mounted onboard. This enables the platform's potential use in a wide variety of applications.
TL;DR: In this paper, a position control of a three degree-of-freedom (d.o.f.) parallel link manipulator using ER (electro-rheological) valve actuators is presented.
Abstract: This paper presents a position control of a three degree-of-freedom (d.o.f.) parallel link manipulator using ER (electro-rheological) valve actuators. Following the composition of an ER fluid consisting of chemically treated starch particles and silicon oil, Bingham model of the ER fluid is empirically obtained as a function of electric fields. Three sets of cylindrical ER valves are then manufactured, and field-dependent pressure drops and response time are evaluated. A three d.o.f. closed-loop parallel link manipulator activated by ER valves bridge circuits is constructed, and its governing equations of motion for heave, roll and pitch are derived using Lagrange equation. Subsequently, sliding mode controllers are formulated by considering nonlinear characteristics of the system and also parameter uncertainties due to the load change on the platform. Computer simulation and experimental implementation of the controllers are undertaken in order to demonstrate effective position tracking responses of the proposed control system. In addition, a comparative work for tracking responses between the sliding mode controller and PID controller is made.
TL;DR: In this article, the authors discuss the design and experimental validation of two controllers for a prototype machine tool axis, actuated by a linear motor: an H1 controller and a discretetime sliding mode controller.
Abstract: This paper discusses the design and experimental validation of two controllers for a prototype machine tool axis, actuated by a linear motor: an H1 controller and a discretetime sliding mode controller. Robustness of the tracking performance with respect to load changes up to 300% is considered. Experiments show that the discrete-time sliding mode controller is robustly performant in this load range. The H1 controller based on standard weighing functions is not robustly performant for the considered range of load changes. This paper proposes an alternative performance weighing function, inspired by the sliding mode controller, which yields an H1 controller with improved robust performance, comparable to that of the sliding mode controller. 7 2000 Elsevier Science Ltd. All rights reserved.
TL;DR: A neural network with fuzzy inference (fuzzy neural network, FNN) presented can effectively improve the learning speed of the neural network for real-time self-reaction of a mobile robot in unknown environments.
Abstract: In this paper, a hybrid intelligent method including fuzzy inference and neural network is presented for real-time self-reaction of a mobile robot in unknown environments. A neural network with fuzzy inference (fuzzy neural network, FNN) presented can effectively improve the learning speed of the neural network. The method can be used to control a mobile robot based on the present motion situations of the robot in real-time; these situations include the distances in different directions between the obstacles and the robot provided by ultrasonic sensors, the target orientation sensed by a simple optical range-finder and the movement direction of the robot. Simulation results showed that the above method can quickly map the fuzzy relationship between the inputs and the output of the control system of the mobile robot.
TL;DR: In this article, a friction drive-type precision actuator which is capable of high positioning accuracy was developed by using piezoelectric elements to anticipate dynamic behavior, system modeling was performed by using stick-slip friction models such as classical, Karnopp, and reset integrator.
Abstract: A friction drive-type precision actuator which is capable of high positioning accuracy was developed by using piezoelectric elements. To anticipate dynamic behavior, system modeling was performed by using stick-slip friction models such as classical, Karnopp, and reset integrator. Dynamic characteristics over various types of driving input signals and driving conditions were investigated by simulation and experiment. By varying phase angle difference and amplitude of driving inputs, it was found that it is possible to control the moving direction and distance of the slider. From simulation and experimental results, it was observed that the dynamic behavior of the simulation predictions agreed well with that of experimental results. This indicates that the model developed in this study is applicable to many other precision mechanisms in which driving friction force is generated by ellipsoidal motion.
TL;DR: In this paper, a hot air jet was used to cut a plate glass profile with a high-quality surface finish, which is the first step in the fabrication for any of its applications.
Abstract: Glass is an important engineering material used in several applications because of its attractive look, chemical stability towards environment, nonporosity, and transparent nature. Its application is widely found in optomechatronic systems, windows of buildings, art work, etc. Glass cutting is the first step in the fabrication for any of its applications. Conventionally, plate glass (soda lime glass) is cut by a diamond point tool or a diamond wheel. The cut surfaces by this method are rough and wavy. Microcracks, which affect the life and quality of glass, may develop during cutting. It is difficult to cut nonstraight profiles by the conventional method and glass wastage is more. Curved profiles cannot be cut in a single step. Recently, glass cutting using laser and abrasive waterjet have been developed. Laser cutting is very costly, unsafe and leaves a heated-affected zone. Researchers have used laser cutting on glasses of thicknesses lesser than 1 mm. Abrasive waterjet requires de-ionized very high pressure water with entrained garnet abrasive. This method produces rough cut surfaces and causes wear of diamond nozzles. A novel method is developed which uses a low cost, simple, hot air jet to cut any complex profile with ease. Experimental studies are conducted to determine the variation of the cutting speed for various values of the stand-off distance, glass thickness, air temperature, and air flow rates. Glasses in the thickness range of 2–20 mm are used for the experiments. The roughness of the cut surfaces using the hot air jet and the diamond point tool is compared. The new method has produced cut surfaces of relatively higher surface finish.
TL;DR: A signal processing algorithm is developed and explained which enables reliable interlace detection, and is effective against diametric noise, and also at high-speed/low-resolution.
Abstract: This paper deals specifically with interlace measurements of intermingled, false-twist textured yarns. A system has been built which is capable of analysing yarns at slow-speed/high-resolution, and also at high-speed/low-resolution. An outline description of the system is given here, along with descriptions of techniques used in the hardware and software which improve the system performance. To monitor interlace, a signal processing algorithm is developed and explained which enables reliable interlace detection, and is effective against diametric noise. Several tests are carried out, which prove the ability of the system to match the results from careful manual inspection of the yarn. The final test is to run the yarn at a high speed, and to compare the results with the slow-speed analysis. The results show that at high speeds, the system is reliable.
TL;DR: The developed algorithms can find application in sports, 3D computer animation and motion analysis of mechanical constructions, as well as an assessment of its performance.
Abstract: The current gait analysis methodology requires tracking of markers placed on the body segments of the lower extremities, by using multiple camera images while the subject is walking This study was aimed at the development of application software for the multicamera marker based gait analysis system established at the Middle East Technical University The main functions of this software are pixel grouping, marker detection and generation of three-dimensional (3D) marker trajectories The software removes noise and artefacts, and effectively detects the physical markers which may be closely spaced and even overlapped on some camera images Then, the images in different cameras are matched by utilising the concept of epipolar lines, and 3D co-ordinates of markers are determined for each matching group at every field Finally, matching of each marker in successive fields is accomplished by employing a set of extrapolation algorithms, thus yielding the required 3D marker trajectories This paper presents theory, algorithms and implementation of the developed software, as well as an assessment of its performance In addition to gait analysis for clinical and research purposes, the developed algorithms can find application in sports, 3D computer animation and motion analysis of mechanical constructions
TL;DR: The computation of information from lines is accurate enough and although the robot has not previous map, it is autonomous when moving in this environment and supposes advantages in comparison with other works because neither image nor camera-wheel calibration are required.
Abstract: In this paper, we study an uncalibrated monocular vision system based on lines for robot navigation in man-made environments Neither environment a priori map is used nor euclidean reconstruction obtained The method is based on the extracted straight lines, supposing the robot moves on a plane ground The effect in the image of camera rotation is computed from the homography of the line at infinity From corresponding vertical lines in two uncalibrated images both, the robot heading and a region in the image, which correspond to the free space ahead, are computed This is the most relevant aspect of our method, because usually it has been considered that corresponding lines in two images do not constraint the structure and motion problem However, using the visibility constraint and compensating the camera rotation, we have obtained the direction of translation and a qualitative free space ahead A control scheme in image coordinates has been implemented to carry out the experiments with our robot moving in the lab It allows the robot to advance along a corridor avoiding doors or pillars without collision The computation of information from lines is accurate enough and although the robot has not previous map, it is autonomous when moving in this environment The method supposes advantages in comparison with other works because neither image nor camera-wheel calibration are required
TL;DR: In this paper, a new accelerometer based on the principle of area-changed capacitance is presented, where the movable mass is designed as many bars connected together and suspended by elastic beams, and two comb-shaped fixed electrodes with their fingers side by side are alternately placed under the mass.
Abstract: A new accelerometer based on the principle of area-changed capacitance is presented. The movable mass is designed as many bars connected together and suspended by elastic beams. Two comb-shaped fixed electrodes with their fingers side by side are alternately placed under the mass. The mass moves in the direction parallel with the substrate plane under the effect of acceleration. The bars and fixed electrodes fingers compose a differential capacitor unit. A quasi-LIGA technology is used to fabricate the sensor chip. And a linear differential capacitance related with the acceleration is obtained.
TL;DR: The proposed structure for open, hierarchical, multi-device controllers takes into account that the system may contain several robots of different types, a certain number of cooperating devices, diverse sensors and also the fact that the task, the system has to execute, and the number and type of its components may vary considerably over time.
Abstract: The paper proposes a structure for open, hierarchical, multi-device controllers. The proposed structure takes into account that the system may contain several robots of different types, a certain number of cooperating devices, diverse sensors and also the fact that the task, the system has to execute, and the number and type of its components may vary considerably over time. The concept has been verified by designing a controller for a prototype Robot of a New Type (RNT) robot. The flexibility of the system is due to the software, so the programming aspect is treated comprehensively in the paper.
TL;DR: In this article, a three-link manipulator mounted on a mobile platform is used to track the horizontal fillet seam in the grillage assembling method, which is one of the conventional procedures for assembling the flat hull blocks in shipbuilding.
Abstract: The mobile platform-manipulator welding system discussed in this paper is a three-link manipulator mounted on a mobile platform. This system uses laser range sensors to guide the mobile platform and a vision sensor to guide the manipulator end-effector to the weld seam line accurately. The task is to track the horizontal fillet seam in the grillage assembling method, which is one of the conventional procedures for assembling the flat hull blocks in shipbuilding and consists of only the horizontal fillet seam. In this paper, the path planning for the combined motion of the mobile platform and the manipulator was presented concerning manipulability measure and characteristics of the welding process. A control method for the mobile manipulator was presented, and simulation results were also presented to demonstrate the effectiveness of the control method for horizontal fillet welding.
TL;DR: In this article, the authors introduce the concept of hybrid five-bar linkages for trajectory generation and make a classification on the hybrid five bar linkages under the condition that no dead point position exists in the linkages.
Abstract: Hybrid machines are driven by two types of motors, namely the real-time non-adjustable (RTNA) motor which provides the majority of driving power and the real-time adjustable (RTA) motor which acts as a low power motion modulation device. Such a configuration has a high operational speed and high load-bearing capacity, and is relatively cheap and can provide flexibility required in many industrial applications. This paper introduces the concept of hybrid five-bar linkages for trajectory generation. A classification is made on the hybrid five-bar linkages under the condition that no dead point position exists in the linkages. The motion range of each class is then studied. An optimal synthesis scheme is put forward based on the criterion which aims at minimizing the maximum power requirement of the RTA motor for a given output motion range. A modified genetic algorithm is used to obtain the global optimal solution. Finally, an example is demonstrated to provide a justification of the proposed ideas and synthesis procedures for the hybrid five-bar linkages.