Installation of passivity on the skin and inside joints of the robotic hand becomes a key-technology to remarkably enhance the stability of handling and manipulation. Based on this idea, in this paper a sophisticated mechanism design of TWENDY-ONE hands with mechanical springs in DIP and MP joints and whole-part covered soft skins is presented.
In this paper, we present a design method of tactile sensors for highly dexterous robotic hands. They are necessary for recognition of volume and softness of a grasped object as well as improvement of handling and manipulation. We also reports experiments demonstrating object recognition based on somatic sensation information detected with them and applications to robust control.
When we make an artificial hand pinch an object by the multiple fingers we need to obtain some information of the object's physical quantity, especially the mass and its location for stable pinching. This paper proposes a method for estimating them for the pinching by two fingers that have soft finger tips and four tiny pressure sensors equipped in the sole of each soft tip. The mass and its location are estimated by the proposed formula with using the value and their variation obtained from the four sensors. This paper also proposes a simple lattice model of the springs to model the soft tip. The experimental results are compared with the simulation results.
Generally, human hands are more dexterous and powerful than robot hands. It is very difficult that robot hands obtain these characteristics simultaneously. The hydraulic remote drive system may have the possibility to satisfy this requirement. A plunger pump was connected to a cylinder mounted in a finger. The cylinder output force is exaggerated by the cross section area ratio of the cylinder and the plunger. The diameter of the cylinder was limited to 10 mm. The experimental data shows that the plunger diameter is limited to 2 mm by the buckling characteristic. The maximum force exaggerating ratio was to 25.
Some environmental contact tasks by a manipulator need large static force. Especially, Accurate positioning of heavy objects needs large force and accurate motion of manipulator. First, we proposed, analyzed and produeced a novel end-effector for a small manipulator to generate large force, that is for 3-D.O.F. pushing operation in 2-dimensional surface. Then, we estimated the movement of object. Simulation results show the effectiveness.
In this paper, we discribe a prototype finger mechanism of an anthropomorphic robot hand with 3D-cam joints. In the previous development, a finger joint is driven by a motor through wires and gears or by compressed air through tubes and so on. These actuation methods, however, have some problems; such as creeping a wire, requirement of large space for an air-compressor, and backlash of gears, which are difficult to solve. The 3D-cam joint we developed has a benefit of extremely low backlash and an ability of self-adjustment for easily assembling a joint structure.
In this paper, we controlled a robot hand using compact ultrasonic motors having 20 degrees of freedom. The robot hand has five fingers with 20 joints. Size and weight are reduced by using compact ultrasonic motors. A robot hand imitating size of human hand can be used as slave hand in master-slave system viscerally. A purpose of this study is confirming availabilities of the robot hand by building up control system. Step response is conducted and frequency response is measured. Then grasping experiment and experiment as a master-slave system are conducted. From these experiments availabilities of the robot hand is confirmed.
This paper presents a mechanical system that achieves grasping, unfolding, and placing motion of fabrics in series. Fabric setting process by human consists of grasping, unfolding, and placing motion of fabrics. We realize the setting process using a single-armed robot and a four degrees of freedom gripper hand. The robotic gripper wrinkles the fabric to make a grasping area using residual deformation of the fabric. In unfolding motion, we introduce a pinching slip motion, that fingertips slip on the fabric surface with grasping, similar to human unfolding motion of fabrics.
We propose a tactile sensor unit for distributed perception. The unit measures and processes tactile information rapidly using a field programmable gate array (FPGA). Additionally, the unit can select any measurement point of 256 points and select the whole sensing element also. The feature of the proposed unit is that the degree of freedom of the measurement is high. In this paper, we describe the drive circuit of the unit and experimental results.
A multi-fingered universal robot hand has been developed in order to construct the platform of humanoid hand study. The special feature of the hand is a miniaturized friction generation mechanism that is installed in the joint driving mechanism. This design has a good effect on sustaining a large external force by a small finger mechanism with a singular point posture.
Artificial hands should be able to perform preshaping and consequent adaptive grasps with high power, and the goals should be realized with a compact and light weighted actuation system to be attached to an arm. Underactuation in one approach to the issue, and several mechanism of such have been proposed. The paper proposes a design of underactuation for wire-driven anthropomorphic hands. Evaluation of actuator configurations within the hand, and the ability of preshaping and adaptive grasping are given.
Tactile sensors are necessary for robotic hand to achieve manipulation under complex environment, such as we often exploit the inner surface even on our hand/finger joints to manipulate edgy objects (e.g. a string). Unfortunately, conventional robotic hands/fingers have no tactile sensors on the hand/finger joints because of limitation of their mechanism. In this paper, we propose a novel mechanism of robotic finger which eases implementation of tactile sensors on the joints; i.e. it allows us to implement tactile sensors seamlessly on the finger surface. We experiment our finger mechanism and show its capability of sensing an edgy object; it is sufficient to be used for manipulation.
We propose a mixed design of machine elements and control systems which aims at avoiding metal fatigue in two-inertia systems. On the basis of an elementary knowledge of material mechanics and machine design, we derive an allowable torsional angle of rotary shafts. Using the ciritical control design framework and the method of inequalities, we design both the diameter of shafts and a feedback controller so as to bound the torsional angle within the allowable value and achieve satisfactory closed-loop performance. An iterative design procedure using bisection algorithm and numerical nonlinear optimization is developed. We finally give a numerical example to evaluate the proposed mixed design method.
PID control is generally used to control mechanical systems. PID control, however, has a limit of accuracy because of the influence of gravity, friction, and interaction of joints. This is caused by modeling error. Digital acceleration control has robustness for the modeling error. Therefore, digital acceleration control is more effective than PID control. But it requires position, velocity, and acceleration of a controlled object to construct a controller. Information of velocity and acceleration cannot be always obtained in mechanical systems.Furthermore, it is desirable that the number of sensors is reduced for the purpose of cost and maintenance. To solve these problems we use ESDS, which is a nonlinear filter based on sliding mode technique. ESDS enables digital acceleration control without increasing the number of sensors. In this paper, we show the results of the proposed control method by using a perpendicular 1-link and 2-link manipulator.
In order to build programs of behavioral decision for autonomous mobile robots, various type of algorithms based on dynamics, geometry, statistics and so on have been adopted. However, there are several difficulties to develop such algorithms. In this paper, as an approach to building programs for autonomous robots, the extraction of human decision rules and the implementation of them to the robot are described. We have developed the immersive remote control system, which can give an operator the physical feature of the robot virtually, and analyzed the human operation by floor area projected onto the screens and joystick command. The robot to which an operator's skill is transferred exhibits similar patterns of motion to the operator's. Furthermore, the robot can adapt to inexperienced environment and drive autonomously.
In collision avoidance in a double-arm robot is focused on. One robot arm (Robot2) is taken as a moving obstacle and another arm (Robot1) should move from a start position to the goal one while avoiding the collision with Robot2. A comparatively short path can be searched efficiently in configuration space (C-space), i.e., joint angle space, by using Rapidly-exploring Random Tree (RRT) method. In this study, to cope with unknown obstacle's trajectory, real-time RRT method is proposed. This method assumes that the robot can obtain the information of unknown object movement at every interval. The robot predicts future obstacle's trajectory based on the information obtained before and now, and generates the trajectory avoiding the collision with the predicted trajectory based on the RRT search within the interval. Both in the simulation and the experiment, the proposed real-time RRT method effectively worked for collision avoidance.
This paper points out that there is another singular point with Coulomb friction when an end effecter of a robot manipulator contacts a surface of an object. The characteristics of Coulomb friction singular points are revealed by both of theoretical and numerical approaches. From the results, it is shown that contact forces dramatically increase as the robot closes Coulomb friction singular points. In this paper we also propose a new control method to overcome problems of Coulomb friction singular points. The effectiveness of the proposed method is demonstrated by some simulation results.
In this paper, we propose a multivariable state and disturbance observer for a SCARA-type planer two-link robot arm with elastic reduction gears, which is treated as a serial two-link two-inertia system. We have already proposed the accurate estimation method for the physical parameters of the two-link arm. The proposed observer is designed by using the physical parameters that include motor inertias, link inertias, joint-friction coefficients and joint-spring coefficients. The off-line estimates using the data of the two-link arm have shown the effectiveness of the proposed observer.
This paper proposes a new method to form motions for multi-joint robots. In the proposed method, several basis motions are obtained thorough iterative learning control without estimating of the parameters of robot dynamics at first. Next, torque patterns which can generate many different motion patterns are easily calculated from the basis motions by using time-scale transformation. Through some experimental results, the effectiveness of the proposed method is demonstrated in this paper.
This paper develops the method for motion planning based on dynamic property of underactuated manipulators that have one actuated joint and some underactuated joints with brakes. First, this method separates motion into conveyance and assembly. As regards assembly, path tracking control method using gravity and on-off control of brakes is suggested. Then initial orientation for assembling motion that makes the control method possible is cleared. And as regards conveyance, algorithm for on-off control of brakes to realize the initial orientation for assembling motion in consideration of interference with objects is suggested. Finally results of simulations and experiments using the method for motion planning that consists of these two motions are shown and its efficacy is clarified.
This paper presents a new energy saving control method for multi-joint robots. The purpose of the proposed control method is to generate periodic motions without using actuator torque as much as possible. To solve this problem, stiffness adaptation(SA) and delayed feedback control(DFC) are simultaneously used. Even though the original DFC requires priori knowledge of objective systems, the proposed control method works without using parameters of the objective systems. Numerical simulation shows that the proposed control method can generate a periodical motion requiring almost no actuator torque in a steady state.
This paper presents a new moving control method about obstacle avoidance problem with prediction time for autonomous omni-directional mobile robot. This method is based on the virtual potential approach and a modified repulsive potential function is proposed. In the method, to avoid obstacles efficiently, the repulsive force is generated by considering the velocity of the obstacle relative to the robot and the prediction time. To verify the effectiveness of the proposed method, the experiments using a robot were carried out. From the results, it was confirmed that the variety of behavior is generated by adjusting the prediction time.
A golf swing robot which has a smart structure and enables high-speed swing based on dynamic coupling drive has been developed by authors. We have reported the feasibility of an energy control method to generate the golf swing trajectory from address position to impact position by adopting target dynamics. In this paper,we apply a new energy control method to generate the whole swing trajectory and show its effectiveness through experimental results.
The respective autonomous mobile robots need to recognize the changes in the environment accurately to accomplish the tasks effectively. In order to realize that, it is significant to predict the movements of the surrounding obstacles. This study proposes a prediction method of the moving objects of the robot's surroundings. The method uses only the information from the sensors on the robot, and thereby can be applied to many kinds of autonomous mobile robots without path planning and self-localization. At first, this paper introduces a method that the robot can estimate moving objects velocity, position, and own velocity. In addition, this paper proposes a method which can control the autonomous mobile robots' behavior using the extended fuzzy potential method from the prediction results. The effectiveness of the method was verified by using the soccer robots of RoboCup Middle-Size-League.
Recently, several soft actuators have been researched because of their high safeties. In this paper, firstly, we designed several types of multi lumen tube actuators made of silicone rubber with Finite Element Method. After that we compared these actuators with evaluation indexes we defined. From this result, we decided the optimum shape of the actuator. The optimized actuator can get large deformation. Secondly, we developed the actuator based on the result of analysis. The actuator has multi lumen structure which causes large deformation of the actuator. It's named Improved Tetra Chamber Actuaotr.We made a basic experiment of this actuator. Finally, we applied several actuators to mechanism which can transport some object. This device has ability of transportation.
A pneumatic system has several advantages, which are cheapness, lightweight, and reliability to human and environment. However, the driving pneumatic actuators require many peripheral devices such as compressor, control valve, and air tube. The purpose of this research is simplification of the pneumatic system. The pneumatic valve used in this system is designed to work corresponding to specific pneumatic vibrator superimposed in the air supply line. This pneumatic system realizes a new driving method to control specific pneumatic actuator without control wire. This system is effective to the system having many degrees of freedom. The principle is confirmed from dynamic simulation and experiment. In the experiment, the experiment model is developed and applied to pneumatic system for driving two pneumatic cylinders. The system works successfully to control two cylinders independently.
Magnetic adsorption device is the one of the important technological elements indispensable for the development of the robot industry, for example, the wall climbing robot. But, the important problem is that the adsorptive power decreases remarkably on the any convex part, any rivet and any welding part, as compared on a flat iron side. For solving this problem, the movable yoke, as according to the magnetic flux changing, is set in the steady yoke where a permanent magnet was fixed. As a result, the big adsorptive power is obtained such as on the convex part. Moreover, the movable yoke returns to initial posture after separating. The report shows that the new mechanism generates a strong magnetic adsorptive power by using Steady yoke and Movable yoke on the ruggedness iron plate.
The passive dynamic control ("PDC") is a new mechanical system control method based on inherently safe design. In this note, the PDC is applied to a pneumatic system and its effectiveness and possibility are shown by experiments of PDC rotary pneumatic actuator equipped with an electromagnetic friction brake and a torque sensor.
Pneumatic actuators have lower environmental load compared with hydraulic actuators. Moreover, pneumatic actuators can achieve compliance and flexibility easily. These advantages make pneumatic actuators used in the fields of medical treatments and industries. However, they have a difficulty in positioning, and impacts on the cylinder ends are big when the actuators are driven with high speed. This study aimed at a development of a new mechanism of a variable orifice driven by PZT. In this report, the oscillator has been improved from the previous prototype to realize flow construe under wide range of pressure. As a result, the performance of the oscillator is greatly improved, and the continuous flow control under high pressure becomes possible.
Recently, there are increasing needs for high power micro actuators in order to downsize the mechatronics devices. The purpose of this paper is to design a new type of micro ultrasonic motor which has a micro encoder. This motor is a rectangular prism with side-lengths 2.6mm, 2.6mm and 9.8mm. The micro encoder mounted on the ultrasonic motor is a magnetic type. This micro encoder was united with a motor shaft and a magnetic drum has 10 poles by 0.43mm pitch. This encoder outputs 20 pulses every revolution. To evaluate this encoder, the revolution speed of the electromagnetic motor was controlled.
The purpose of this study is to develop a contractile pneumatic rubber muscle which has a high contraction rate. The developed rubber muscle is constructed an expansion rubber unit and a nylon band. Since the expansion rubber unit is put between the nylon band, the expansional displacement of the expansion unit is converted to the contractile one by the nylon band. In this paper, the structure of the developed rubber muscle is discussed, and then the characteristics of this muscle are described.
As robots expand into the society, it is necessary for robots to move safely for avoiding injury on impact. External force measurement is vital to move safely depending on the situation. Many methods for measuring torque are to measure strain of the elastic body. Measurement accuracy and tortional stiffness of the elastic body are in a trade-off relation. Accuracy improvement requires to reduce the tortional stiffness of torque sensor, but it makes dynamic characteristic of the joint complex. By joint structure specializing in measuring torque and canceling five-axis force other than joint torque, this paper proposes a mechanism to establish torque control with the use of rigid torque sensor with higher resolution.
A novel pneumatic cylinder is proposed, named Magnetic Brake Cylinder, abbreviated to MB Cylinder. It is composed of a tank, a cylinder, and a permanent magnet, and with this, the piston is held by the magnet's attractive force until the pressure inside the tank is very high, offering a higher driving power than an ordinary cylinder when using the same pressure source. In addition, a control method of its driving power is introduced. The developed MB Cylinder is then mounted into two types of rescue inspectors: a rolling and jumping rescue robot, which uses a cylinder to jump over obstacles, and a throw and collect rescue inspector, which deploys with the cylinder a child machine over high obstacles. Both developed prototypes showed higher jumping and throwing height than when using an ordinary cylinder, proving to be an option of effective enhancement of traversing ability for pneumatically powered robots.
Cantilevered electromagnetic actuators are simple on structure and operation, while its mobility region is strictly limited due to pull-in instability. To extend the mobility region, a novel open loop oscillatory control method which does not need sensors has been presented. In this method, although the current applied to the coil is usually a direct current, an alternating current is superimposed onto the direct current. However, the vibration is generated in the magnet by applying an alternating current. Then, in this study, we adjust the input alternating current to control the vibration. Therefor we use numerical simulation to examine the relation between input frequency and pull-in instability to get critical frequency. In addition, we examine the relation between the input frequency and the amplitude of magnet confirming the simulation result by the experiment.
This paper reports the development of thin straight fibers type artificial muscles. The straight fiber types of artificial muscle have greater contraction ratio and power and a longer lifetime than McKibben types. And the thin straight type artificial muscle is a micro miniaturization of the straight type artificial muscle that is examined ahead in this laboratory. It has the outside diameter of 1.2 millimeters and the inside diameter of 0.5 millimeters. Therefore it can work in a limited space. For example, it is expected that the muscles would be used for the direction control in the point part of industrial endoscopes.
An ultra precision positioning actuator with large force and long stroke has been proposed. This actuator is driven by piezoelectric(PZT) actuators. In order to design the actuator which utilizes the large force of PZT actuator, it is necessary to design the actuator which has high stiffness. But there are many factors which decrease this stiffness, such as manufacturing error, contact deformation, clearance between its output link and clamp, individual difference of PZT actuator's length. Then, mechanisms which adjust these factors and an actuator with these mechanisms have been proposed. Besides, driving method which increases output force by increasing the number of driving PZT actuators at the same time has been proposed. Basic characteristics of the proposed actuator and driving methods have been experimentally investigated.
This paper presents a method for mechanical stiffness control of the antagonistically driven joint using the ANLES(Actuator with Non-Linear Elasticity). This system fundamentally mimics a skeletal muscle. It requites a non-linear elastic body similar to human muscles. At first an antagonistically driven joint mechanism using the ANLES is described. It follows to show the basic formula for controlling the stiffness and the posture of the multi-D.O.F. joints by multiple-ANLES. Subsequently, this paper shows results of the position control and the stiffness control of 3.D.O.F. It is scheduled to make new structure of 3.D.O.F. wrist joint for an anthropomorphic robot from results of these
This paper discusses feasibility of the high powered piezoelectric diaphragm pump used as the miniature actuator for industrial robot grippers. Utilization of high power and high response of piezoelectric elements for the pump is considered to realize the miniature actuator. Dynamic characteristics of the prototyped pump have been measured and analyzed. From experimental results of frequency responses of flow volume and output pressure and analytical results, it has been clarified that stiffness of the diaphragm against pressure in the pump greatly influences the performance of the pump.
This paper presents an artificial muscle, which is composed of ECF-jet driven micro cells. This artificial muscle can arbitrarily specify the contraction length and force by changing the number of integrated cells. The cell consists of a jet generator, a shrinkage part, and a tank. The size of the micro cell is φ12.5mm x 13mm. With serial connection of cells, the total contraction length may be the sum of each cell's contraction and the force may be the average of each force. On the other hand, with parallel connection, the contraction length may be the average of each cell's contraction and the force may be the sum of each force. The maximum contraction and force of the cell integrated ECF artificial muscle (2x2) are 2.80mm and 504.1mN, respectively, at an applied voltage of 8kV.
This research will be realizing Human Adaptive Mechanism for Physical Human Machine interaction by applying several intelligent pneumatic cylinders. Each cylinder consists of optical encoder, force sensor,valve and controlled by PSoC as the central processing unit. PSoC will handle I2C communication, input and output data from ADC, counter and PWM module. Four types of control approaches were used and done experimentally towards realizing the final goal which is position servo control, force control, compliance control and viscosity control. By applying these control approach, the intelligent cylinders have the ability to detect objects with different stiffness and damping characteristics for future Intelligent Chair Tool.
We propose the Pseudo Mechanism scheme. Force feedback control enables back-drive of a worm gear, which naturally cannot be back-driven because of it mechanical stop feature. If the feedback control is switched on or off according to the conditions, its mechanical feature can be shifted from pseudo back-drivable characteristics to natural non-back-drivable characteristics. For example, if the force feedback control is applied only when the force is positive, this system allows the positive rotation and negative rotation is prohibited as a one-way clutch. The compensation method of friction loss of a worm gear is also tested.
In this research, the power source of SMA actuator is light energy which can be used under specific environment. The SMA actuator is driven by heat. Fabricated SMA actuator can be driven under specific environment by converting light energy into thermal energy. Additionally, optical adhesive was used for an energy transmission method from light source. The actuator consisted of a substrate, a SMA, an optical waveguide and an optical fiber. The length of the driving part was 45mm. The uniform heating of the actuator was realized by using a patterned gold thin film. The displacement value of SMA actuator is 4.2mm and the generated force by SMA actuator was 35mN when the irradiated optical output was 0.39W.
Today, some kinds of robots are developed which used nearby daily living of human. The backdriveability is important to act according to user's movement for such robots. We want to develop a linear actuator of high power and backdriveability. In this paper,we aim to create a new ER gel linear actuator by reviewing the ER gel linear actuator developed last year.
We have proposed the tailor-made multilayer piezoelectric actuator (TAMPA) with large displacement and large force. The TAMPA has the layered structure of two bimorph-type piezoelectric elements combined by both ends supported. Therefore, the performance of TAMPA is affected by the shape and the stiffness of support. It is necessary to design the optimum structure of support of TAMPA. This paper proposes four-point supported structure because of the plate shape of bimorph-type piezoelectric elements. And the effect of the shape of supports is estimated through finite element analysis of TAMPA constructed by four-point support of varied sizes. TAMPA having the optimum structure determined from estimation result is produced and its performance is evaluated. For production, the mold made by rapid prototyping is utilized. It is possible to produce the support which had arbitrary shape by using this mold.
Nation based precious metal plating ionic polymer metal composite(IPMC) actuator is very attractive because of its high-speed response and softness of the material. The positioning control of IPMC was generally thought very difficult because the initial deformation rapidly disappeared. In the author's former research, however, IPMC's positioning control could be done by applying the residual deformation. It was very important to keep the direction of the residual deformation to the same direction to the initial deformation. In the previous report, we found that 0.1% NaOH solution extend the period of the IPMC's residual deformation to be the same direction to the initial deformation. We expected that 0.1% NaOH solution could prevent the leakage of Na^+ positive counter ion. In this study, however, we knew from experimental results that the direction of the residual deformation was determined by the pH of the negative ion that contained in the counter ion introducing solution. We discussed the deformation mechanism of the IPNIC based on the experimental results.
This report deals with an application of a small mobile device, "AZARASHI(seal) Mechanism" with three degrees of freedom(DOFs) to a micromanipulation device. AZARASHI mechanism has a smaller number of controlled devices than the inchworm-like device. The small device with multiple DOFs is able to be built by using this mechanism. A micromanipulation device consists of an L-shaped device for the x, y and θ-motions, and one-DOF device in the z-motion. By the visual feedback, a glass bead is placed automatically. To hold a glass bead with a diameter of 60-70μm, the air was gently vacuumed through the glass capillary. Then the bead is picked and placed after moving the device. Finally, the bead has placed. The performance of the manipulation device was measured.
Flexible actuation is required for robot actuators used in environment with uncertainties. Conventionally, flexibility is realized either by control or mechanical elasticity. These methods have following problems; lack of high responsiveness and lack of high stiffness. To solve these problems, backdrivability is necessary for robot actuators. Backdrivablity is obtained by using hydrostatic transmission. But hydraulic circuit with hydrostatic transmission may have cavitation which decrease the control performance. In this paper, first anti-cavitation mechanism is presented. Next, the performance of miniature robot actuator with anti-cavitation mechanism is shown.
This paper proposes a new flexible fluid linear actuator we call Lambda-Drive. This actuator is composed of a flat-section tube and slider that keeps the tube lambda(Λ) shape. The tube is occluded at lambda shape point, and pressure in the tube provides force at the point, then slider moves by the force without high friction. The author shows how to move Lambda-Drive and measure the output force. The author applies the Lambda-Drive to a zip fastener and makes an active fastener that moves itself to pull up and pull off. This new actuator is very simple but high efficient and applicable to various equipments.
This paper presents a prototype of variable stiffness unit which utilize component of force of linear springs. The principle of the variable stiffness is described. The mechanism and control unit of the prototype are illustrated. The experiments are examined and the effectiveness is confirmed.