Linearization, Advanced Digital Control, State Controller

tt.DDL: Dynamic Digital LinearizationNanometer Trajectory during Dynamc ScansImproved Piezo Control:Dynamic Digital Linearization(DDL)Conventional piezo controllerscannot completely avoid phaseshiftand tracking errors in applicationswith rapid, periodicmotion. This is due in part tothe non-linear nature of thepiezoelectric material, the finitecontrol bandwidth and the inherentlimitations of P-I (proportional-integral)servocontrol,which only reacts whena position error is detected. TheDDL option (ordering numberE-710.SCN), available withrecent digital piezo controllerssuch as E-753 (single-channel,see p. 2-108) or E-712 (multichannel,see p. 2-140), solvesthis problem. This technology,developed by PI, reduces theerror between the current anddesired position to impercep -tible values. The dynamiclinearity and effectively usablebandwidth are thus improvedby up to three orders of magnitude.DDL is of benefit to singleandmulti-axis applicationswhere motion follows a giventrajectory repeatedly (seemeasurement curves).Ordering InformationE-710.SCNFirmware Upgrade DDL(Dynamic Digital Linearization)Available for controllers:E-712, E-725 and E-753.notice.Nanopositioning systems with conventional PID controller:Single axis movement with a 312 Hz triangular signal. Thedifference between target and actual position can be up to 2.6 µm.Elliptical scan with a XY piezo scanner and conventionalP-I-servo controller. The outer curve shows the desiredposition, the inner curve shows the actual motion.Connt erol(PI)0ectKGalmeitrugstDik In9G/06.mb2H2EysiSubj& Coo2BRO1© Phch ange without009Nanopositioning system with DDL option: The same single axismovement as above, with 312 Hz triangular signal. The differencebetween target and actual position is practically unobservable andis about 7 nanometers.The same scan as before but with a DDL controller.The tracking error is reduced to a few nanometers,desired and actual position cannot be distinguished inthe graph.W W W . P I . W S

tt.APC: Advanced Piezo ControlAlternative Control Concept for Faster SettlingTransient response of ansystem with optimated PIDparameters (blue) andAdvanced Piezo Control (pink).An alternative control concept The phase trueness is signifi-Ordering Informationis available for the modular cantly improved compared toE-712 controller for nanoposi- the damping with one or even E-712.U1Firmware Upgrade Advancedtioning systems: Advanced two notch filters. This hasPiezo ControlPiezo Control. It is based on a immediate effects on the trajecstatecontroller which, in turn, is tory trueness and the settling Advanced Piezo Control is alsoavailable for the E-753based on a model of the posi- response.(1 Channel) and for the E-725tioning system.(3 Channels). Ask your PI SalesLimitations of theDepartment.Advanced Piezo Control Advanced Piezo Controlactively damps the resonance If the mechanical system hasfrequency, in contrast to con- too many resonances closeventional PID controllers with together, or if the resonancenotch filter where the mechani- frequency to be damped iscal resonance is cut out of the about 1 kHz or more, the stateexcitation spectrum.controller in this form no longerhas any advantage over con-APC: Advanced Piezo Controlventional PID controllers.Faster and More StablePlease discuss your applicationThe consequences are faster with us.settling times and lower sensitivitywith respect to interferencesfrom the outside.Connt erol(PI)0ectKGoch200ange without9almeitrugstDik In2Eysi9G/06.mb2HSu&BRO1© PhbjConotice.Bode plot of an unloaded, Bode plot of a closed loop system with Bode plot of an system controlledopen loop system with two one notch filter at the first resonance. with Advanced Piezo Control. Theresonance frequencies.resonances are better suppressed, thephase deviation is lower compared tothe suppression with a notch filter.W W W . P I . W S