Watch out, Tiger Woods![golf playing robot]

This article describes the development of an autonomous robotic system for playing mini-golf. The system was designed and built to serve as a demonstration of robotic application for engineering students. The system was built using a Yasakawa robot fitted with two arms. The software was developed to control the machine using the C++ language. Standard C++ libraries were used in addition to communication libraries provided by the Yasakawa Corporation. The current configuration works with Microsoft Windows NT and an Ethernet environment. This article describes the hardware and software design aspects of this machine.     

Design and characterization of a low-profile micropositioning stage

This paper discusses the design and characterization of a new, single-axis, low-profile, piezo-driven vertical motion micropositioning stage for use in laser welding applications. A low-profile configuration is attained by mounting the piezo actuator horizontally and using a novel lever arrangement to transfer the horizontal motion of the actuator into the desired vertical motion. An analytical model for the static and dynamic behavior of the stage is presented, along with finite element (FE) modeling verification. A 200 μm motion-range stage was built, and tests show that the stage has a vertical stiffness of 6.0 N/μm and a resonance frequency of 364 Hz. The results are in very close agreement to those predicted by the model.     

A force sensing tool for disassembly operations

This paper discusses the design and characterization of a prototype disassembly tool that was designed to handle a family of electronic devices whose plastic, cantilever snap-fit covers house AA or AAA batteries. The tool was designed with the ability to release the snap-fit covers and the batteries contained inside. The tool design is based on the use of a force sensing tool tip that utilizes three force sensing resistors (FSRs) for force feedback. Two FSRs were used to measure horizontal forces applied to the tool tip while the third FSR was used to measure forces along a direction normal to the tool tip. The tool tip is used to push and lift up the snap-fit cover as well as the spring-loaded batteries. By using the conductance of the FSR sensors, a linear model of the FSR output was calibrated to the force applied to the FSR. The disassembly tool was mounted on a three-axis translational motion robot, and the robot was programmed to perform disassembly operations. Sensor feedback from the FSRs was used to control the movement of the tool during these operations. The results showed that the robot was able to successfully use the disassembly tool to perform the necessary operations to remove the device's snap-fit cover and batteries. Force readings recorded from the FSRs indicated that the disassembly tool was able to react to force interactions at the disassembly tool tip such as a missing part or misaligned part. The use of FSRs resulted in a low-cost, flexible disassembly tool.     

Generalized preisach model for hysteresis nonlinearity of piezoceramic actuators

This paper presents a new approach for modeling the hysteresis nonlinearity of a piezoceramic actuator using a modified generalized Preisach model, and the use of this model in a linearizing control scheme. The developed generalized Preisach model relaxes the congruency requirement on the hysteresis loops of a piezoceramic actuator, which must be satisfied when using the classical Preisach model. The congruency property is experimentally proved to not hold when running the actuator on a minor hysteresis loop. A numerical expression of the model is derived in terms of first- and second-order reversal curve experimental datasets. Output prediction using this model is performed on both an exponentially decayed sinusoidal input signal and an arbitrary input signal, and the results show that the model can accurately reproduce the hysteresis response with an error of less than 2.7%. A tracking control system for a piezoceramic actuator is also developed by combining a PID feedback controller with a hysteresis linearizing scheme in a feed-forward loop. The results show that this new control system can achieve 0.25 μm tracking control accuracy, which is 80 and 50% less than that obtained when using an open-loop controller and a regular feedback control system, respectively.     

A manufacturing system for automated production of polystyrenemolds

A compact automated system cuts complicated contours on prefabricated polystyrene blocks which are used as molds to cast Cerrobend, which is used as a shield in radiation therapy. The authors describe the development of the prototype, including details for machine configuration, motion planning and cutting experiments     

Measuring workpiece dimensions using a non-contact laser detector system

Proper process control procedures are important considerations in the optimisation of any manufacturing process. Ultimately, a continuous update on the size and quality of the products being manufactured is desirable. A non-contact laser detector system was developed to measure the dimensions of wood products in a real-time operating environment, employing a two-axis lateral effect photodiode as the sensor. Computer algorithms were developed to measure the thickness, warp, and width of wood samples (pencil slats). The effect of mechanical vibration due to slat transport was identified and when possible eliminated. The system was evaluated at different transport speeds. The results indicated that, except for width measurement which is limited by the computing speed, the system can measure thickness and warp quite accurately at feed speeds of 240 feet per minute. Although the work described is specific to certain applications, the implications for use in other industrial activities where visual sensing is required is apparent.     

Abstraction database concept for engineering modeling

Engineering modeling and design generally involve a large set of independent but interrelated data items. One way to organize and store these data items in a systematic and consistent manner is through the use of a database management system. The abstraction concepts of aggregation and generalization provide a powerful mechanism for organizing and structuring engineering data. The invariants required to maintain the abstract data model are examined in this paper. Integrity issues involved in the data representation of hierarchically structured engineering models, such as constructive solid geometry models, are discussed. Object-oriented programming concepts are used to implement a prototype integrity subsystem for enforcement of integrity constraints in the aggregation/generalization framework for modeling data.     

Modeling of flexure-hinge type lever mechanisms

A general approach for the design of flexure-hinge type lever mechanisms that are commonly used in the design of translational micro-positioning stages is presented in this paper. The paper focuses on the development of design equations that can accurately predict the behavior of such stages especially the “lost motion” due to hinge stretching. The development of these equations is based on a static analysis of a general configuration of a single-axis, translational, flexure-hinge type, piezo-driven micro-positioning stage using a multi-lever structure. The displacement ratio between the input and output motions of one of the levers, plus the stiffness at either end of this lever are obtained based on the analysis. The overall displacement and stiffness of the micro-positioning stage are then obtained by cascading the individual results from every lever. The developed equations include the effects of the flexure hinge bending and stretching. The developed equations were applied to design of a vertical motion micro-positioning stage. The stiffness and displacement of this stage are predicated by these equations, which are compared to the stiffness and displacement directly obtained from the finite element modeling and actual testing of the same micro-positioning stage. The comparison shows that the analytical approach gave nearly similar results (within 10%), which implies that the developed equations can accurately predict the characteristics of flexure-hinge type lever mechanisms.     

A system for automated disassembly of snap-fit covers

This paper reports on a prototype automated system for the disassembly of batteries from a family of electronic devices whose plastic, snap-fit covers house AA or AAA batteries, such as remote controls and calculators. Included in the development of the prototype system was the design of a disassembly tool that uses three force-sensing resistors to provide force feedback information. A pneumatically actuated vacuum gripper and electromagnet system was also developed for recovering the snap-fit cover and batteries once they were released by the disassembly tool. The disassembly module was mounted on the tool head of a three-axis translational motion robot, and a Visual Basic application was developed to interface and control the robot with a Galil digital motion controller. A model-based computer vision application was also developed in Visual C++ using a Kinect sensor and the Open Source Computer Vision library to identify and localize the electronic device placed on the disassembly robot. Using the information gathered by the model-based computer vision application, the robot was able to use the disassembly tool module to perform the necessary disassembly operations to remove the device’s snap-fit cover and batteries. The design of such a disassembly system could aid the future development of fully autonomous disassembly systems that can handle a broader range of electronic products.     

Design and characterization of a precision fluid dispensing valve

Precision fluid dispensing is a complicated but yet relevant process where fluid is dispensed in a controlled manner. It is important and applicable in an array of applications ranging from dispensing of food products, biomedical applications to dispensing of adhesive and encapsulants in the semi-conductor industry. This paper discusses the design and characterization of a precision fluid dispensing hybrid valve based on the time-pressure, positive displacement pump, and adhesive jetting technologies. The main advantage of this dispensing method is that the amount of fluid dispensed is independent of the standoff height and does not rely on surface tension between the substrate and the fluid for clean dispensation. Specifically, the dispensed fluid is jetted from a fixed needle height, and hence, repeatability and accuracy is improved while eliminating vertical travel. A prototype valve was built and tested for precision and accuracy of milligrams over a range of pressures and time. The test results are promising, indicating high repeatability and accuracy for low to medium viscous materials and are comparable to existing commercially available precision dispensing systems.