Model based friction compensation for an electro- mechanical actuator of a Stewart platform Maarten Willem van der Kooij Friday, November 4 th 2011 TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.:
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Intro – Moog Former Fokker company Located in Nieuw Vennep Employees: Netherlands 160 Worldwide
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Intro – Stewart Platform 3
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Intro – Stewart Platform 4 6 degrees of freedom Electromechanical vs. hydraulic actuators
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Intro – Friction 5 Friction opposes the direction of relative velocity
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Intro – Current method 6 Simplified model ‘Moog’ compensation
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Overview 7 Friction Phenomena Friction Models Friction Model ID Measurement Set-up System Identification FFWD Compensation Adjustments Theory Identification Implementation Conclusions
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Theory – Friction Phenomena 8
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Lund-Grenoble model Force equation State equation where Theory – Friction Models 9
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Theory – Friction Models DNLRX model Presliding model Sliding model 10
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Overview 11 Friction Phenomena Friction Models Friction Model ID Measurement Set-up System Identification Theory Identification
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Identification – Measurement Set-up 12
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Equation of Motion 1.System Identification including simple friction model 2.Identify friction in nonlinear region Identification – System Identification 13
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Identification – Friction Model Identification 14
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Identification – Check 15
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Overview 16 Friction Phenomena Friction Models Friction Model ID Measurement Set-up System Identification FFWD Compensation Adjustments Theory Identification Implementation
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Implementation 17 Comparison of three situations Standard test cycle signal Sinusoidal signal 0.2 Hz – 20mm amplitude (‘low acceleration’)
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Implementation – Initial Compensation Results 18
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Implementation – Model Adjustment LuGre Reduce compensation when leaving presliding DNLRX Reduce number of parameters 19
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Implementation – Results 20
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Implementation – Results: tracking error 21
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Overview 22 Friction Phenomena Friction Models Friction Model ID Measurement Set-up System Identification FFWD Compensation Adjustments Theory Identification Implementation Conclusions
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Velocity tracking error reduction by 80% on average for Adjusted DNLRX model Adjusted LuGre model Initial DNLRX model by 69% on average for Initial LuGre model The current is predictable with an absolute average error of 0.1 A Further work is needed on Influence of load Influence of actuator orientation 23
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Questions? 24 ?
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Appendix Slides 25
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions LuGre Adjusted 26
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Control of the Actuator / Platform 27
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Position Control 28
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Derivation of the equation of motion 29
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Commanded Velocity Tracking Improvement 30
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions 31/… System Model
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions System Identification Static Model 32
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions DNLRX Dynamic Non Linear Regression with direct application of eXcitation Cost function used in optimization 33
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Implementation – ‘Moog’ Algorithm 34 Two tuning methods Manual Automatic
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Prediction error 35
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions System Identification 36
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Validation Data Set 37
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Motor Cogging 38
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Motor Cogging 39
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Acceleration, vel, Tff 40
Model based friction compensation for an electromechanical actuator of a Stewart platform Theory Identification Implementation Conclusions Copper losses i^2 * R Iron losses (magnetic losses) Hysteresis losses (magnetization of ferromagnetic materials) Eddy current losses Mechanical losses 41 Losses in the motor