Linear actuator

Abstract: Using the linear forces that are provided by an electromagnetic solenoid applied near the distal end of a medical catheter (26), various surgical instruments can be actuated or deployed for use in interventional medicine. The linear actuator (101) uses the principles of magnetic repulsion and attraction as a means for moving a bobbin (13) that can be attached to various types of moving components that translate linear movements into the actuation of a tool that is attached to the linear actuator. Using independent solenoid coils (14), movement modality is increased from two possible positions to three.

Abstract: Series elastic actuators have linear springs intentionally placed in series between the motor and actuator output. The spring strain is measured to get an accurate estimate of force. A second order linear actuator model is broken into two fundamental cases: fixed load-high force (forward transfer function), and free load-zero force (impedance). This model is presented with dimensional analysis and extends previous linear models to include friction. Using the model and dimensionless groups, we examine nonlinear effects of motor saturation as it relates to large force bandwidth and nonlinear friction effects such as stiction. The model also helps to clarify how the springs help and hinder the operation of the actuator. The information gained from the model helps to create a design procedure for series elastic actuators. Particular emphasis is placed on choosing the spring constant for the elastic element.

Abstract: Preface. Introduction. I. FUNDAMENTALS. 1 Fluid Properties. 1.1 Introduction. 1.2 Fluid Mass Density. 1.3 Fluid Bulk Modulus. 1.4 Thermal Fluid Properties. 1.5 Fluid Viscosity. 1.6 Vapor Pressure. 1.7 Chemical Properties. 1.8 Fluid Types and Selection. 1.9 Conclusion. 1.10 References. 1.11 Homework Problems. 2 Fluid Mechanics. 2.1 Introduction. 2.2 Governing Equations. 2.3 Fluid Flow. 2.4 Pressure Losses. 2.5 Pressure Transients. 2.6 Hydraulic Energy and Power. 2.7 Lubrication Theory. 2.8 Conclusion. 2.9 References. 2.10 Homework Problems. 3 Dynamic Systems and Controls. 3.1 Introduction. 3.2 Modeling. 3.3 Linearization. 3.4 Dynamic Behavior. 3.5 State-Space Analysis. 3.6 Block Diagrams and the Laplace Transform. 3.7 Stability. 3.8 Compensation. 3.9 Conclusion. 3.10 References. 3.11 Homework Problems. II HYDRAULIC COMPONENTS. 4 Hydraulic Control Valves. 4.1 Introduction. 4.2 Valve Flow Coefficients. 4.3 Two-Way Spool Valves. 4.4 Three-Way Spool Valves. 4.5 Four-Way Spool Valves. 4.6 Poppet Valves. 4.7 Flapper Nozzle Valves. 4.8 Conclusion. 4.9 References. 4.10 Homework Problems. 5 Hydraulic Pumps. 5.1 Introduction. 5.2 Pump Efficiency. 5.3 Gear Pumps. 5.4 Axial-Piston Swash-Plate Pumps. 5.5 Conclusion. 5.6 References. 5.7 Homework Problems. 6 Hydraulic Actuators. 6.1 Introduction. 6.2 Actuator Types. 6.3 Linear Actuators. 6.4 Rotary Actuators. 6.5 Conclusion. 6.6 References. 6.7 Homework Problems. III HYDRAULIC CONTROL SYSTEMS. 7 Valve-Controlled Hydraulic Systems. 7.1 Introduction. 7.2 Four-Way Valve Control of a Linear Actuator. 7.3 Three-Way Valve Control of a Linear Actuator. 7.4 Four-Way Valve Control of a Rotary Actuator. 7.5 Conclusion. 7.6 References. 7.7 Homework Problems. 8 Pump-Controlled Hydraulic Systems. 8.1 Introduction. 8.2 Fixed-Displacement Pump Control of a Linear Actuator. 8.3 Variable-Displacement Pump Control of a Rotary Actuator. 8.4 Conclusion. 8.5 References. 8.6 Homework Problems. INDEX.

Abstract: Dr. D. Yang, Dr. M. S. Verma, Dr. J.-H. So, Prof. B. Mosadegh, Prof. C. Keplinger, B. Lee, F. Khashai, E. Lossner, Prof. G. M. Whitesides Department of Chemistry and Chemical Biology Harvard University 12 Oxford Street , Cambridge , MA 02138 , USA E-mail: gwhitesides@gmwgroup.harvard.edu Dr. D. Yang, Prof. Z. Suo School of Engineering and Applied Sciences Harvard University 29 Oxford Street , Cambridge , MA 02138 , USA Prof. B. Mosadegh, Prof. G. M. Whitesides Wyss Institute for Biologically Inspired Engineering Harvard University 60 Oxford Street , Cambridge , MA 02138 , USA Prof. Z. Suo, Prof. G. M. Whitesides Kavli Institute for Bionano Science & Technology Harvard University 29 Oxford Street , Cambridge , MA 02138 , USA