Design and manufacturing of mobile micro manipulation system with a compliant piezoelectric actuator based micro gripper

This paper presents a new design of mobile micro manipulation system for robotic micro assembly where a compliant piezoelectric actuator based micro gripper is designed for handling the miniature parts and compensation of misalignment during peg-in-hole assembly is done because piezoelectric actuator has capability of producing the displacement in micron range and generates high force instantaneously. This adjusts the misalignment of peg during robotic micro assembly. The throughput/speed of mobile micro manipulation system is found for picking and placing the peg from one hole to next hole position. An analysis of piezoelectric actuator based micro gripper has been carried out where voltage is controlled through a proportional-derivative (PD) controller. By developing a prototype, it is demonstrated that compliant piezoelectric actuator based micro gripper is capable of handling the peg-in-hole assembly task in a mobile micro manipulation system.     

Development of Multi Micro Manipulation System Using IPMC Micro Grippers

This paper presents a new design of multi micro manipulation system using ionic polymer metal composite (IPMC) micro grippers for robotic micro assembly where IPMC is used as a light weight actuator for developing the micro grippers. It has the potential of large displacement, low mass force generation and misalignment compensation ability during micro manipulation. These capabilities are utilized for handling of miniature parts like pegs. The analysis of IPMC micro gripper and manipulator are carried out for developing a multi micro manipulation system that can handle pegs in micro assembly operation for shifting one to another hole position in a large work space (100 mm × 100 mm). By developing a prototype, it is demonstrated that IPMC based micro grippers are capable of handling the peg-in-hole assembly tasks in a multi micro manipulation system.     

Three methodologies for the calibration of industrial manipulators: Experimental results on a SCARA robot

This article presents and compares three algorithms for the geometric parameter identification of industrial robots to increase its accuracy (static calibration). The estimation is based on the measure of the gripper pose errors when the robot follows suitable trajectories. The algorithms are general and can be applied to any robot providing that its kinematics is known. After a theoretical introduction to the general methodologies, these are applied to a selective compliance assembly robot arm (SCARA) robot analyzing its performance (precision, efficiency). Experimental results obtained with three methodologies are presented and discussed. The measure of the gripper pose error is based on a laser triangulation technique whose working principles are also recalled. © 2000 John Wiley & Sons, Inc.     

基于IPMC 驱动的自主微型机器鱼

本文从微小型鱼类的运动和受力分析入手,基于人工肌肉IPMC（离子聚合物金属复合材料）的特性, 进行微型机器鱼的结构和控制系统的设计．在此基础上实现仿小型鱼类的各种运动模式,然后,讨论了IPMC 驱动 器推进效率的优化．实验结果证明,基于IPMC 的厘米级机器鱼是可行的：通过改变控制信号的频率和占空比,实 现微型机器鱼的速度控制;通过控制胸鳍和尾鳍,实现上浮、下潜、转弯、巡游等运动模式．最后从尾鳍推进器的结 构角度分析了如何提高推进效率．     

Intelligent robotic gripper with adaptive grasping force

The on-off control robot gripper is widely employed in pick-and-place operations in Cartesian space for handling hard objects between two positions. Without contact force monitoring, it can not be applied in fragile or soft objects handling. Although, an appropriate grasping force or gripper opening for each target could be searched by trial-and-error process, it needs expensive force/torque sensor or an accurate gripper position controller. It has too expensive and complex control strategy disadvantages for most of industrial applications. In addition, it can not overcome the target slip problem due to mass uncertainty and dynamic factor. Here, an intelligent gripper is designed with embedded distributed control structure for overcoming the uncertainty of object’s mass and soft/hard features. A communication signal is specified to integrate both robot arm and gripper control kernels for executing the robotic position control and gripper force control functions in sequence. An efficient model-free intelligent fuzzy sliding mode control strategy is employed to design the position and force controllers of gripper, respectively. Experimental results of pick-and-place soft and hard objects with grasping force auto-tuning and anti-slip control strategy are shown by pictures to verify the dynamic performance of this distributed control system. The position and force tracking errors are less than 1 mm and 0.1 N, respectively.

     

Micro parts assembly system with micro gripper and RCC unit

This paper presents a new micro assembly system, which is composed of a micro gripper, a micro remote center compliance (RCC) unit, a voice coil motor-driving mechanism and precision motion stages. The micro gripper is actuated by two shape memory alloy (SMA) wires, and its grip is 1 mm. The micro RCC unit has low translational and rotational stiffness sufficient for micro parts assembly. The voice coil motor-driving mechanism can generate linear motion with an adjustable stiffness, and it can also measure external force in the moving direction. An algorithm for the automatic assembly of micro parts is also proposed, and assembly experiments are performed.     

基于分层控制的移动机器人最优运动规划

研究移动机器人在带有多移动障碍物的动态环境中的运动规划问题，基于分层最控制理论，提出了一种新的运动规划方法来解决移动机器人的导航与避障问题，仿真实例证明了该方法的有效性。     

Assembly and measuring technique for the manufacturing of active micro systems

This paper presents the current results of the development of an assembly equipment with integrated measuring system that will permit a high position accuracy. The kernel of the work is an parallel robot, an innovative optical sensor for 3 dimension and an micro gripper.     

A compliant end-effector coupling for vertical assembly: design and evaluation

Many manipulation tasks require compliance, i.e. the robot's ability to comply with the environment and accomplish force as well as position control. Examples are constrained motion tasks and tasks associated with touch or feel in fine assembly. Few compliance-related tasks have been automated, and usually by active means of active compliance control: the need for passive compliance offered by the manipulator itself has been recognized and has led to the development of compliant end-effectors and/or wrists. In this paper we present a novel passively compliant coupling, the compliant end-effector coupling (CEEC), which aids automated precision assembly. It serves as a mechanical interface between the end of the robot arm and the end-effector. The coupling has 6 degrees of freedom. The design of the coupling is based on a “lock and free” assembly idea. The coupling is locked and behaves like a stiff member during robot motion, and is free (compliant) during constrained motion. It features an air bearing, a variable stiffness air spring and a center-locking mechanism. The end-effector assembly, being centrally unlocked, will float within the designed compliance limits assisted by the air bearing. These frictionless and constraint-free conditions facilitate a fast correction of any initial lateral and angular misalignments. In a peg insertion assembly, such accommodation is possible provided that the tip of the peg is contained within the chamfer of the hole. A variable stiffness air spring was incorporated in the design to allow variable and passive vertical compliance. This vertical compliance allows the accommodation of angular and vertical errors. The center-locking mechanism will return the end-effector assembly to its initial position upon an error correction. In a robot application program, the CEEC can be locked during rapid motion to securely transport a part or be set free during assembly or disassembly processes when the motions are constrained.     

二自由度SCARA机器人位置的端口受控哈密顿与反步法协调控制

针对二自由度SCARA机器人系统使用单一控制方法难以实现快速、精准的位置跟踪控制的问题,设计了基于端口受控哈密顿(PCH)与反步法的协调控制.PCH用于保证系统稳态性能,反步法用于保证系统快速性.采用指数函数作为协调函数以实现协调控制策略,从而适应二自由度SCARA机器人的轨迹跟踪控制.该SCARA机器人系统,既能够实现系统快速的跟踪位置信号,又能够提高系统的输出信号的稳态性能.仿真实验表明,当存在干扰时,采用PCH与反步法的协调控制的二自由度SCARA机器人位置跟踪系统能够有效地结合两者的优点,系统的动态性能和稳态性能优良,且能够很好地抵抗外部干扰.     

A servo-controlled robot gripper with multiple sensors and its logical specification

The logical specification of a microprocessor-based air-servo-controlled robot hand is presented, as well as its actual implementation. This hand can accommodate a wide variety of workpieces and allows for flexible assembly through the use of an automatic quick-change fingertip. The changeable set of gripper fingers is equipped with sensors, including a tactile force sensor, a crossfire sensor, a proximity sensor, and a slip sensor. A changeable set of gripper fingers with different sensing ranges can cope with certain subranges of the workpiece spectrum. A considerable cost saving is achieved by not changing the gripper itself. This specially designed hardware and software system includes position and force feedback. A PUMA 560 is used to test the success of the entire process.     

Two robot arms in assembly by using impulsive information

When two robot arms execute coordinated motions in assembly, collision between the two end-effectors cannot be avoided. The collision effects on the two coordinating robots include two aspects: abrupt velocity changes of the robot joints and impulsive forces exerting on the contact point as well as on robot joints. Since the direction of the impulsive force exerting on the contact point is related to the relative position and orientation of the two mating parts, the impulsive force can be used to detect the alignment errors of the two end-effectors. Thus a new assembly method is proposed in this article. The new method uses impulsive information to adjust the position and orientation errors of the two robot arms in assembly, rather than employing a compliance mechanism. The advantage of the new method is that the jamming problem, which is usually associated with compliance methods, never takes place. To make the method practically useful, wrist force sensors are suggested to installed at the wrist of each robot. Dynamic relations between the sensed information and the impulsive force at the contact point are then established. The sensed information thus becomes useful in analyzing the alignment situation. Finally, practical cases are studied to illustrate the use of the new assembly method.     

Micro assembly in a SEM chamber and the solution for collision prevention

As the micro assembly becomes more and more important, it is necessary to make it reliable and expeditious. In this paper the scope is on the micro assembly in the chamber of the scanning electron microscope during which a micro gripper approaches the specimen holder and the micro components positioned on it are picked up. The current design of equipment in the SEM chamber does not allow an assessment of the position in the z-direction that causes that tips of micro grippers could break if they collide with the specimen holder. Here is described the video system consisted of micro camera with the magnifications lenses and mess stripe, which enables accurately watching the approaching to the micro components and exact calculation of the distance between micro gripper and the micro component.     

Robotic assembly automation using robust compliant control

Industrial robots used to perform assembly applications are still a small portion of total robot sales each year. One of the main reasons is that it is difficult for conventional industrial robots to adapt to any sort of change. This paper proposes a robust control strategy to perform an assembly task of inserting a printed circuit board (PCB) into an edge connector socket using a SCARA robot. The task is very challenging because it involves compliant manipulation in which a substantial force is needed to accomplish the insertion operation and there are some dynamic constraints from the environment. Therefore, a robust control algorithm is developed and used to perform the assembly process. The dynamic model of the robotic system is developed and the dynamic parameters are identified. Experiments were performed to validate the proposed method. Experimental results show that the robust control algorithm can deal with parameter uncertainties in the dynamic model, thus achieve better performance than the model based control method. An abnormal case is also investigated to demonstrate that the robust compliant control method can deal with the abnormal situation without damaging the system and assembly parts, while pure position control method may cause damages. This strategy can also be used in other similar assembly processes with compliant applications.     

Velocity Estimation for Robot Manipulators Using Neural Network

In robot manipulators, optical incremental encoders are widely used as the transducers to monitor joint position and velocity information. With incremental encoder, positional information is determined as discrete data relative to a reference (home) position. However, velocity information can only be deduced by processing the position data. In this paper, a method of using a neural network to estimate the velocity information of robotic joint from discrete position versus time data is proposed and evaluated. The architecture of the neural net and the training methodology are presented and discussed.This approach is then applied to estimate the joint velocity of a SCARA robot while performing an electronic component assembly task. Based on computer simulations, comparison of the accuracy of the neural network estimator with two other well established velocity estimation algorithms are made. The neural net approach can maintain good performance even in the presence of measurement noises.     

Error Detection and Prediction Algorithms: Application in Robotics

This article presents research on error detection and prediction algorithms in robotics. Errors, defined as either agent error or Co-net error, are analyzed and compared. Three new error detection and prediction algorithms (EDPAs) are then developed, and validated by detecting and predicting errors in typical pick and place motions of an Adept Cobra 800 robot. A laser Doppler displacement meter (LDDM™) MCV-500 is used to measure the position of robot gripper in 105 experiment runs. Results show that combined EDPAs are preferred to detect and predict displacement errors in sequential robot motions.     

A self-centering electrostatic microgripper

Automated microassembly of micro hybrid devices is one fundamental step to reduce their high cost. Often, microassembly deals with fragile and wear-sensitive microparts that must be accurately grasped, positioned, and released or fastened in stable positions. The requirements of reliable, flexible, and fast assembly devices are other important characteristics to be achieved. This paper deals with the design of an electrostatic gripper that can grasp standard microcomponents and delicate mini and micro parts alike. The aim of this work is to theoretically and experimentally demonstrate the good performance of a self-centering gripper based on electrostatic forces. This paper extends previous works concerning electrostatic handling by adding new theoretical and FEM models, further tests, and new interpretations of the gripper’s grasping and centering capabilities. The design of the gripper is justified and supported by theoretical considerations. To better evaluate the generated force and the influences of the component on the gripper performance, FEM models are presented.     

Universal compliant device based on SCARA concept

The paper presents the results of the research and the development of the universal adaptive compliant device for customary assembly task robot configurations. The developed system is based on a newly developed SCARA robotic mechanism and combined properties of the SCARA concept and RCC devices. It successfully operates around its true compliance center, obtained under precisely determined conditions.     

Design of a self-adaptive gripper with rigid fingers for Industrial Internet

Grippers are widely used in Industrial Internet for facilitating various operations such as logistics, materials handling, assembly, etc. Current grippers are specifically designed for a specific application so that it is difficult to adapt to a wide variety of shapes and sizes. Soft grippers have been developed to grasp objects with high surface complexity in Industrial Internet. Some challenges such as low controllability and long response time still exist. Rigid robot gripper shows good characters like robustness, accuracy and short response time. This paper thus presents a robot self-adaptive gripper using rigid fingers, where four rigid fingers are connected by springs that are tied to a screw rod. The screw rod is actuated by a rotary motor. Tip force of the fingers could be precisely controlled by the linear movement of the screw rod. The shapes and sizes of the object could be adaptively grasped due to the elasticity of the connecting springs. The proposed gripper is tested and verified to be highly flexible and controllable so that it could be suitable for most of the applications in production systems in the context of Industrial Internet.     

Static calibration of industrial manipulators: Design of an optical instrumentation and application to SCARA robots

This article presents a method for the static calibration of industrial robots based on optical measurements using a laser. Measured pose errors are used to estimate the geometric errors in the links. This allows the prediction of the pose error for every robot configuration, permitting the improvement of accuracy by means of slight variations of the joint motions. After a theoretical introduction on the methodology, it is applied to a SCARA robot analyzing the design of the set-up and the final precision that could be achieved. Preliminary experimental results are also presented. © 1996 John Wiley & Sons, Inc.