8.SMA-Control

Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 111Dr. SongDaLian University of Technology 8. Control Design for Shape Memory Alloy Systems -- An Introduction Shape Memory Alloy Wire Actuator LVDT Position Sensor Current Amplifier Bia Spring Linear Bearing Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 222Dr. SongDaLian University of Technology EXPERIMENTAL SETUP • The Single Wire Test Stand – Nickel-Titanium SMA wire (30.48 cm in length and 0.381 mm in diameter). – dSPACE Data Acquisition and Real Time Control system Shape Memory Alloy Wire Actuator LVDT Position Sensor Current Amplifier Bia Spring Linear Bearing Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 333Dr. SongDaLian University of Technology Task1: Position Regulation using Sliding-mode Based Robust Control Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 444Dr. SongDaLian University of Technology CONTROL SYSTEM DESIGN • Define: e y y= − d i i i r r= + − −b f Dk Tanh aρ a f r e e= +� λ • Robust Tracking Controller : a linear feedback action functioning as a Proportional plus Derivative (PD) control. : a bias current. To compensate for the hysteresis of the SMA wire actuator and environmental heat losses. −kD r if − ρTanh a ra f : a robust compensator and to compensate for the hysteresis to increase control accuracy and stability Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 555Dr. SongDaLian University of Technology Low Pass Filter KD Robust Comp. R G ai n Command Saturation Feedback Signal Command Signal Programmable Power Supply Real-Time Control System Bias t ∂ ∂ λ LVDT Sensor The Control Block Diagram Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 666Dr. SongDaLian University of Technology Experimental Result • The position of the actuator is required to move from 0mm to 12mm. • The controller parameters are: λ = 5, KD = 1, ρ = 1, and a = 5 . The feedforward value is .4. With Robust Control • RMS error of 0.0233mm Settling time = 1.3 second 5 10 15 20 25 30 0 5 10 15 20 25 30 -1 0 1 2 3 4 5 6 7 Figure 5 Displacement with Robust Control Figure 6 Control Action with Robust Control Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 777Dr. SongDaLian University of Technology Without Robust Control • RMS error of 0.1241mm • Settling time = 2.4 second 0 5 10 15 20 25 30 -1 0 1 2 3 4 5 6 7 0 5 10 15 20 25 30 2 0 2 4 6 8 0 2 4 Figure 7 Displacement without Robust Control Figure 8 Control Action without Robust Control Experimental Result Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 888Dr. SongDaLian University of Technology Experimental Result With Robust Control The SMA wire undergoes both heating and cooling processes 0 5 10 15 20 25 30 -2 0 2 4 6 8 10 12 14 0 5 10 15 20 25 30 -1 0 1 2 3 4 5 6 7 Figure 9 Displacement with Heating & Figure 10 Control Action with Heating & Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 999Dr. SongDaLian University of Technology Conclusion • A novel robust controller based on sliding-mode approach is developed for precision position regulation of a SMA wire actuator. • Experiments were conducted and successfully demonstrated that shape memory alloy actuators with the proposed control design can be used for precision position regulation . Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 101010Dr. SongDaLian University of Technology Task2: Position Tracking using Sliding-mode Based Robust Control 0 20 40 60 80 100 120 5 6 7 8 9 10 11 12 13 Time (s e cond) p o s i t i o n ( m m ) Dotted line : de s ire d pa th; S olid line : a c tua l pos ition Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 111111Dr. SongDaLian University of Technology PRELIMINARY TEST 0 50 100 150 200 0 1 2 3 4 Dotte d line : App lie d vo lta ge (V) S o lid line : App lie d c u rre n t (A) 0 50 100 150 200 -1 0 1 2 3 4 5 6 7 8 9 Tim e (s e c ond) D i s p l a c e m e n t ( m m ) 0 0 .5 1 1 .5 -1 0 1 2 3 4 5 6 7 8 9 C urre n t (A) D i s p l a c e m e n t ( m m ) Input signal Displacement Hysteresis Loop Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 121212Dr. SongDaLian University of Technology CONTROL SYSTEM DESIGN • Define: e y y= − d i i i r r= + − −b f Dk Tanh aρ a f r e e= +� λ • Robust Tracking Controller : a linear feedback action functioning as a Proportional plus Derivative (PD) control. : a bias current. To compensate for the hysteresis of the SMA wire actuator and environmental heat losses. −kD r ib i y yf f d dk T= +( � ) − ρTanh a ra f : a feed-forward term : a robust compensator and to compensate for the hysteresis to increase control accuracy and stability Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 131313Dr. SongDaLian University of Technology This feed forward current is designed to provide the approximate amount of current required for the SMA actuator to follow the desired path. The actuator system with a bias spring is approximately a first order system with a time constant T, if the current is considered as the input and the displacement is considered as the output. The Feed-forward Term i y yf f d dk T= +( � ) Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 141414Dr. SongDaLian University of Technology Remarks • To further decrease the position error, an alternative non-linear sliding surface can be designed as r e e e= + + =� ( )λ c Tanh c1 2 0 where c1 and c2 are positive gains. The goal of the term c Tanh c1 2( )e is to provide a larger magnitude value of r at small value of e to augument the λe term and further decrease the tracking error. The new auxiliary control variable r is an odd function and the stability for the closed-loop system is ensured. Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 151515Dr. SongDaLian University of Technology EXPERIMENTAL RESULTS Desired and actual displacements (1/15 Hz) 0 20 40 60 80 100 120 5 6 7 8 9 10 11 12 13 Time (s e cond) p o s i t i o n ( m m ) Dotted line : de s ire d pa th; S olid line : a c tua l pos ition 0 20 40 60 80 100 120 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 Time (s e cond) P o s i t i o n E r r o r ( m m ) Position Error (RMS error: .063mm) Test 1: Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 161616Dr. SongDaLian University of Technology Test 1: Applied voltage and Current 0 20 40 60 80 100 120 -1 0 1 2 3 4 5 6 Top: Applie d volta ge (V) Bottom : Applie d c urre nt (A) Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 171717Dr. SongDaLian University of Technology Test 2: With Nonlinear Sliding Surface Desired and actual displacement in case of nonlinear sliding surface 0 20 40 60 80 100 5 6 7 8 9 10 11 12 13 Tim e (s e c ond) p o s i t i o n ( m m ) Dotte d line : de s ire d pa th; S olid line : a c tua l pos ition 0 20 40 60 80 100 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 Time (s e c ond) P o s i t i o n E r r o r ( m m ) Position error (RMS error: .046mm) in case of nonlinear sliding surface Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 181818Dr. SongDaLian University of Technology Test 2: Applied voltage and Current 0 20 40 60 80 100 -1 0 1 2 3 4 5 6 Time (s e c ond) Top: Applie d volta ge (V) Bottom: Applie d c urre nt (A) Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 191919Dr. SongDaLian University of Technology Robust Position Control of an SMA Actuator in Water – An Implementation Example Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 202020Dr. SongDaLian University of Technology ADAPTIVE ENGINE INTAKE – An Implementation Example Movie Smart Materials and Structures 8. Control Design for Shape Memory Alloy Systems – An Introduction 212121Dr. SongDaLian University of Technology Conclusions • A novel robust controller based on sliding-mode approach is developed for tracking control of a SMA wire actuator. • Experiments were conducted and successfully. demonstrated that shape memory alloy actuators with the proposed control design can precisely track a reference command.