Design and Implementation of Position Estimator Algorithm on Voice Coil Motor

Voice Coil Motors (VCMs) have been an inevitable element in the mechanisms that have been used for precise positioning in the applications like 3D printing., micro-stereolithography., etc. These voice coil motors translate in a linear direction and require a high accuracy position sensor that amounts for a major part in the budget. In this research work., an effort has been made to design and implement an algorithm that would predict the displacement of VCM and eliminate the need of high cost sensors. VCM was integrated with dSPACE DS1104 R&D controller via linear current amplifier (LCAM) which acts as a driver circuit for VCM. Sine input was given to VCM with various amplitude and frequency and the corresponding displacement is measured by using linear variable differential transformer (LVDT). The position estimator algorithm is also implemented at the same time on VCM and its output is compared with that of LVDT. It is observed that there is 97.8 % accuracy in between algorithm output and LVDT output. Further., PID controller is used in integration with the novel algorithm to minimize the error. The estimator algorithm is tested for various amplitudes and frequencies and it is found that it has a very good agreement of 99.2% with the actual displacement measured with the help of LVDT

Actuators for a space manipulator

The robotic manipulator can be decomposed into distinct subsytems. One particular area of interest of mechanical subsystems is electromechanical actuators (or drives). A drive is defined as a motor with an appropriate transmission. An overview is given of existing, as well as state-of-the-art drive systems. The scope is limited to space applications. A design philosophy and adequate requirements are the initial steps in designing a space-qualified actuator. The focus is on the d-c motor in conjunction with several types of transmissions (harmonic, tendon, traction, and gear systems). The various transmissions will be evaluated and key performance parameters will be addressed in detail. Included in the assessment is a shuttle RMS joint and a MSFC drive of the Prototype Manipulator Arm. Compound joints are also investigated. Space imposes a set of requirements for designing a high-performance drive assembly. Its inaccessibility and cryogenic conditions warrant special considerations. Some guidelines concerning these conditions are present. The goal is to gain a better understanding in designing a space actuator

Multi-level fine pointing test-bed for space applications

For space applications that need high accuracy pointing of the payload, fine pointing system is an indispensable tool. To reach high level of high accuracy pointing and tracking, proper synchronization between the attitude of the satellite and each stage of the pointing module should be considered. This study focuses on developing and demonstrating staging control for fine pointing system. Currently, an experimental model for multi-stage control has been built in the laboratory to be used as a testbed and a teaching tool to validate the control strategies. This paper gives a brief introduction of the study, experimental model design criteria and staging control strategy. An example of a controller synthesis for multi-stage actuators based on Hinfinity is also presented

Design of ultraprecision machine tools with application to manufacturing of miniature and micro components

Currently the underlying necessities for predictability, producibility and productivity remain big issues in ultraprecision machining of miniature/microproducts. The demand on rapid and economic fabrication of miniature/microproducts with complex shapes has also made new challenges for ultraprecision machine tool design. In this paper the design for an ultraprecision machine tool is introduced by describing its key machine elements and machine tool design procedures. The focus is on the review and assessment of the state-of-the-art ultraprecision machining tools. It also illustrates the application promise of miniature/microproducts. The trends on machine tool development, tooling, workpiece material and machining processes are pointed out

Structurally adaptive space crane concept for assembling space systems on orbit

Many future human space exploration missions will probably require large vehicles that must be assembled on orbit. Thus, a device that can move, position, and assemble large and massive spacecraft components on orbit becomes essential for these missions. A concept is described for such a device: a space crane concept that uses erectable truss hardware to achieve high-stiffness and low-mass booms and uses articulating truss joints that can be assembled on orbit. The hardware has been tested and shown to have linear load-deflection response and to be structurally predictable. The hardware also permits the crane to be reconfigured into different geometries to satisfy future assembly requirements. A number of articulating and rotary joint concepts have been sized and analyzed, and the results are discussed. Two strategies were proposed to suppress motion-induced vibration: placing viscous dampers in selected truss struts and preshaping motion commands. Preliminary analyses indicate that these techniques have the potential to greatly enhance structural damping

Development of kinematic equations and determination of workspace of a 6 DOF end-effector with closed-kinematic chain mechanism

This report presents results from the research grant entitled Active Control of Robot Manipulators, funded by the Goddard Space Flight Center, under Grant NAG5-780, for the period July 1, 1988 to January 1, 1989. An analysis is presented of a 6 degree-of-freedom robot end-effector built to study telerobotic assembly of NASA hardware in space. Since the end-effector is required to perform high precision motion in a limited workspace, closed-kinematic mechanisms are chosen for its design. A closed-form solution is obtained for the inverse kinematic problem and an iterative procedure employing Newton-Raphson method is proposed to solve the forward kinematic problem. A study of the end-effector workspace results in a general procedure for the workspace determination based on link constraints. Computer simulation results are presented

Design and application of electromechanical actuators for deep space missions

During the period 8/16/92 through 2/15/93, work has been focused on three major topics: (1) screw modeling and testing; (2) motor selection; and (3) health monitoring and fault diagnosis. Detailed theoretical analysis has been performed to specify a full dynamic model for the roller screw. A test stand has been designed for model parameter estimation and screw testing. In addition, the test stand is expected to be used to perform a study on transverse screw loading

Structural characterization of a first-generation articulated-truss joint for space crane application

A first-generation space crane articulated-truss joint was statically and dynamically characterized in a configuration that approximated an operational environment. The articulated-truss joint was integrated into a test-bed for structural characterization. Static characterization was performed by applying known loads and measuring the corresponding deflections to obtain load-deflection curves. Dynamic characterization was performed using modal testing to experimentally determine the first six mode shapes, frequencies, and modal damping values. Static and dynamic characteristics were also determined for a reference truss that served as a characterization baseline. Load-deflection curves and experimental frequency response functions are presented for the reference truss and the articulated-truss joint mounted in the test-bed. The static and dynamic experimental results are compared with analytical predictions obtained from finite element analyses. Load-deflection response is also presented for one of the linear actuators used in the articulated-truss joint. Finally, an assessment is presented for the predictability of the truss hardware used in the reference truss and articulated-truss joint based upon hardware stiffness properties that were previously obtained during the Precision Segmented Reflector (PSR) Technology Development Program

An Open-Source 7-Axis, Robotic Platform to Enable Dexterous Procedures within CT Scanners

This paper describes the design, manufacture, and performance of a highly dexterous, low-profile, 7 Degree-of-Freedom (DOF) robotic arm for CT-guided percutaneous needle biopsy. Direct CT guidance allows physicians to localize tumours quickly; however, needle insertion is still performed by hand. This system is mounted to a fully active gantry superior to the patient's head and teleoperated by a radiologist. Unlike other similar robots, this robot's fully serial-link approach uses a unique combination of belt and cable drives for high-transparency and minimal-backlash, allowing for an expansive working area and numerous approach angles to targets all while maintaining a small in-bore cross-section of less than $16cm^2$. Simulations verified the system's expansive collision free work-space and ability to hit targets across the entire chest, as required for lung cancer biopsy. Targeting error is on average $<1mm$ on a teleoperated accuracy task, illustrating the system's sufficient accuracy to perform biopsy procedures. The system is designed for lung biopsies due to the large working volume that is required for reaching peripheral lung lesions, though, with its large working volume and small in-bore cross-sectional area, the robotic system is effectively a general-purpose CT-compatible manipulation device for percutaneous procedures. Finally, with the considerable development time undertaken in designing a precise and flexible-use system and with the desire to reduce the burden of other researchers in developing algorithms for image-guided surgery, this system provides open-access, and to the best of our knowledge, is the first open-hardware image-guided biopsy robot of its kind.Comment: 8 pages, 9 figures, final submission to IROS 201

Investigation of feeding devices and development of design considerations for a new feeder for micro-sheet forming

Recent review in micro-forming research and technological development suggested that the trend of the development is more focused on the manufacturing processes, machines and tooling, and efforts on the methods and systems for integrated precision material handling are insufficient. Most of the developed micro-forming machines were based on standalone concepts which do not support efficient integration to make them fully automated and integrated. At present, material feeding in micro-forming is not of sufficient precision and reliability for high throughput manufacturing applications. Precise feeding is necessary to ensure that micro-parts can be produced with sufficient accuracy, especially in multi-stage forming, while high-speed feeding is a must to meet the production-rate requirements. Therefore, design of a new high-precision and high-speed feeder for micro-forming is proposed. Several possible approaches are examined with a view to establishing feasible concepts. Based on the investigation, several concepts for thin sheet-metal feeding for micro-forming are generated, they being argued and assessed with applicable loads and forces analysis. These form a basis of designing a new feeder