Rotary Encoders - HEIDENHAIN
Rotary Encoders11/2017
Rotary encoders from HEIDENHAINserve as measuring sensors for rotarymotion, angular velocity, and when used inconjunction with mechanical measuringstandards such as lead screws, for linearmotion. Application areas include electricalmotors, machine tools, printing machines,woodworking machines, textile machines,robots and handling devices, as well asvarious types of measuring, testing, andinspection devices.The high quality of the sinusoidal incrementalsignals permits high interpolation factorsfor digital speed control.Rotary encoders for separate shaft couplingElectronic handwheelRotary encoder with mounted stator couplingInformation on Encoders for servo drives Sealed angle encoders Modular angle encoders with opticalscanning Modular angle encoders with magneticscanning Linear encoders for numericallycontrolled machine tools Exposed linear encoders Interface electronics HEIDENHAIN controlsis available upon request as well as on theInternet at www.heidenhain.de.2Further information:Comprehensive descriptions of allavailable interfaces as well as generalelectrical information are included in theInterfaces of HEIDENHAIN Encodersbrochure.This brochure supersedes all previouseditions, which thereby become invalid.The basis for ordering from HEIDENHAINis always the brochure edition valid whenthe order is made.Standards (ISO, EN, etc.) apply onlywhere explicitly stated in the brochure.
ContentsIntroductionSelection guideMeasuring principles, accuracyMechanical design types and mountingRotary encoders with stator couplingRotary encoders for separate shaft couplingShaft couplingsGeneral mechanical informationSafety-related position measuring systemsSpecificationsMounted stator couplingSeparate shaft coupling;synchro flangeSeparate shaft coupling;clamping flange4141619242730Absolute rotary encodersIncremental rotary encodersECN 1000/EQN 1000 seriesERN 1000 seriesECN 400/EQN 400 seriesERN 400 seriesECN 400 F/EQN 400 F series–ECN 400 M/EQN 400 M series–ECN 400 S/EQN 400 S series–ECN 400/EQN 400 serieswith fieldbus–46ECN 400/EQN 400 serieswith universal stator couplingERN 400 seriesWith universal stator coupling48ECN 100 seriesERN 100 seriesROC/ROQ 1000 seriesROD 1000 seriesROC/ROQ 400 seriesRIC/RIQ 400 seriesROD 400 series525458ROC 400 F/ROQ 400 F series–66ROC 400 M/ROQ 400 M series–ROC 400 S/ROQ 400 S series–ROC/ROQ 400 serieswith fieldbus–68ROC 425With high accuracy–70ROC/ROQ 400 seriesRIC/RIQ 400 seriesROD 400 series72ROC 400 F/ROQ 400 F series–76ROC 400 M/ROQ 400 M series–ROC 400 S/ROQ 400 S series–ROC/ROQ 400 serieswith fieldbus–ROD 600 series323644788082Separate shaft coupling;fastening by flange/base–ROD 1930Sturdy designHandwheels–HR 112084Interfaces and pin layoutsIncremental signals869198102104Electrical connectionPosition valuesCables and connecting elementsInterface electronicsDiagnostic and testing equipment
Selection guideRotary encoders for standard applicationsRotary EncodersAbsoluteSingleturnInterfaceEnDatMultiturn 4096 FINET IOECN 1013–EnDatFanucMitsubishiSiemensEQN 1035–With mounted stator couplingECN/EQN/ERN 1000 seriesECN 1023–Positions/rev: 13 bitsPositions/rev: 23 bitsEnDat 2.2/22ECN/EQN/ERN 400 seriesPositions/rev: 23 bitsEnDat 2.2/22ECN 1013EQN 1025Positions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsEnDat 2.2/01ECN 425ECN 425 FECN 413–Positions/rev: 25 bits Positions/rev: 25 bits Positions/rev: 13 bitsEnDat 2.2/22Fanuc iAvailable withFunctional safetyECN 425 MEQN 437ECN 413Positions/rev: 25 bitsPositions/rev: 13 bits MitsubishiEnDat 2.2/01EQN 4253)Positions/rev: 24 bitsDRIVE-CLiQAvailable withFunctional safety–ECN/EQN/ERN 400 series withuniversal stator couplingECN 425ECN/ERN 100 series–EQN 436 SPositions/rev:24 bitsDRIVE-CLiQAvailable withFunctional safety–ECN 413––EQN 437–Positions/rev: 13 bits–ECN 413–Positions/rev: 13 bitsPositions/rev: 25 bitsEnDat 2.2/22Positions/rev: 25 bitsEnDat 2.2/22ECN 413EQN 425Positions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsEnDat 2.2/01ECN 125––––Positions/rev: 25 bitsEnDat 2.2/22ECN 113Positions/rev: 13 bitsEnDat 2.2/011)Up to 36 000 signal periods through integrated 5/10-fold interpolation (higher interpolation on request)Voltage supply: DC 10 V to 30 V3)Also available with TTL or HTL signal transmission4)Available with mechanical fault exclusion; for restrictions on specifications and for special mounting information,see the Fault Exclusion customer information document2)DRIVE-CLiQ is a registered trademark of SIEMENS AG.4EQN 435 MPositions/rev:Positions/rev: 13 bits 23 bitsEnDat 2.2/01MitsubishiECN 424 SECN/EQN 400 serieswith fieldbusEQN 437 FPositions/rev: 25 bits Positions/rev:EnDat 2.2/2225 bitsAvailable withFanuc iFunctional safety–
IncrementalSSIPROFIBUS-DPPROFINET IO TTLEQN 1025–ERN 1020ERN 1030ERN 1080100 to3600 lines100 to3600 lines100 to3600 linesPositions/rev: 13 bits HTL 1 VPP32ERN 10701000/2500/1)3600 linesEQN 4253)–Positions/rev: 13 bits4)36ERN 420ERN 430ERN 480250 to5000 lines250 to5000 lines1000 to5000 lines––46448ERN 4602)250 to5000 lines–EQN 425–Positions/rev: 13 bitsEQN 425–Positions/rev: 13 bitsERN 420ERN 430ERN 480250 to5000 lines250 to5000 lines1000 to5000 linesERN 4602)250 to5000 lines––ERN 120ERN 130ERN 1801000 to5000 lines1000 to5000 lines1000 to5000 lines525
Rotary encoders for standard applicationsRotary encodersAbsoluteSingleturnInterfaceEnDatMultiturn 4096 FINET IOROC 1013–EnDatFanucMitsubishiSiemensROQ 1035–For separate shaft coupling, with synchro flangeROC/ROQ/ROD 1000 seriesROC 1023–Positions/rev: 13 bitsPositions/rev: 23 bitsEnDat 2.2/22ROC/ROQ/ROD 400RIC/RIQ 400 seriesWith synchro flangePositions/rev: 23 bitsEnDat 2.2/22ROC 1013ROQ 1025Positions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsEnDat 2.2/01ROC 425ROC 425 FROC 413–ROQ 437ROQ 437 FPositions/rev: 25 bits Positions/rev: 25 bits Positions/rev: 13 bitsEnDat 2.2/22Fanuc iAvailable withROC 425 MFunctional safetyPositions/rev: 25 bitsROC 413MitsubishiPositions/rev: 13 bits ROC 424 SEnDat 2.2/01Positions/rev: 24 bitsPositions/rev: 25 bits Positions/rev: 25 bitsEnDat 2.2/22Fanuc iAvailable withROQ 435 MFunctional safetyPositions/rev: 23 bitsROQ 425MitsubishiPositions/rev: 13 bits ROQ 436 SEnDat 2.2/01Positions/rev: 24 bitsRIC 418RIQ 430DRIVE-CLiQPositions/rev: 18 bits Available withEnDat 2.1/01Functional safetyROC/ROQ 400 seriesWith fieldbus–ROC 425For high accuracyROC 425–DRIVE-CLiQPositions/rev: 18 bits Available withEnDat 2.1/01Functional safety–ROC 413––––ROQ 437ROQ 437 FPositions/rev: 13 bits–––ROC 413–Positions/rev: 25 bitsEnDat 2.2/01For separate shaft coupling, with clamping flangeROC/ROQ/ROD 400RIC/RIQ 400 seriesWith clamping flangeROC 425ROC 425 FPositions/rev: 25 bits Positions/rev: 25 bits Positions/rev: 13 bitsEnDat 2.2/22Fanuc iAvailable withROC 425 MFunctional safetyPositions/rev: 25 bitsROC 413MitsubishiPositions/rev: 13 bits ROC 424 SEnDat 2.2/01Positions/rev: 24 bitsPositions/rev: 25 bits Positions/rev: 25 bitsEnDat 2.2/22Fanuc iAvailable withROQ 435 MFunctional safetyPositions/rev: 23 bits4)ROQ 425MitsubishiPositions/rev: 13 bits ROQ 436 SEnDat 2.2/01Positions/rev: 24 bitsRIC 418RIQ 430DRIVE-CLiQPositions/rev: 18 bits Available withEnDat 2.1/01Functional safetyROC/ROQ 400 seriesWith fieldbus1)––DRIVE-CLiQPositions/rev: 18 bits Available withEnDat 2.1/01Functional safety–ROC 413Positions/rev: 13 bitsUp to 10 000 signal periods through integrated 2-fold interpolationUp to 36 000 signal periods through integrated 5/10-fold interpolation (higher interpolation on request)3)Voltage supply: DC 10 V to 30 V4)Also available with TTL or HTL signal transmission2)6––
IncrementalSSIPROFIBUS-DPPROFINET IO TTLROQ 1025–ROD 1020ROD 1030ROD 1080100 to3600 lines100 to3600 lines100 to3600 linesROD 426ROD 436ROD 4865)50 to1)5000 lines50 to5000 lines1000 to5000 lines–––6870Positions/rev: 13 bits HTL 1 VPP54ROD 10701000/2500/2)3600 linesROQ 425–Positions/rev: 13 bits58ROD 4663)50 to5000 lines2)–ROQ 4254)Positions/rev:13 bits–––––ROQ 425–ROD 420ROD 430ROD 48050 to5000 lines50 to5000 lines1000 to5000 lines–––Positions/rev: 13 bits–ROQ 4255)Positions/rev:13 bits5)7278Mechanical fault exclusion available; for restrictions on specifications and for specialmounting information, see the Fault Exclusion customer information documentDRIVE-CLiQ is a registered trademark of SIEMENS AG.7
Rotary encoders for motorsRotary nDatWith integral bearing and mounted stator couplingERN 1023 64ECN/EQN 1100 seriesERN 1123 00ECN/EQN/ERN 1300 series 40ECN/EQN/ERN 400 series 64–ECN 1113EQN 1135EQN 1125Positions/rev: 13 bitsEnDat 2.2/01Positions/rev: 23 bits4096 revolutionsEnDat 2.2/22Available withFunctional safetyPositions/rev: 13 bits4096 revolutionsEnDat 2.2/01––––ECN 1325ECN 1313EQN 1337EQN 1325Positions/rev: 25 bitsEnDat 2.2/22Available withFunctional safetyPositions/rev: 13 bitsEnDat 2.2/01Positions/rev: 25 bits4096 revolutionsEnDat 2.2/22Available withFunctional safetyPositions/rev: 13 bits4096 revolutionsEnDat 2.2/01ECN 413Positions/rev: 13 bitsEnDat 2.2/01EQN 437Positions/rev: 25 bits4096 revolutionsEnDat 2.2/22Available withFunctional safety8192 signal periods through integrated 2-fold interpolationMechanical fault exclusion available; for restrictions on specifications and for special mounting information,see the Fault exclusion customer information documentDRIVE-CLiQ is a registered trademark of SIEMENS AG.8–ECN 1123Positions/rev: 25 bitsEnDat 2.2/22Available withFunctional safety2)–Positions/rev: 23 bitsEnDat 2.2/22Available withFunctional safetyECN 4251)–EQN 425Positions/rev: 13 bits4096 revolutionsEnDat 2.2/01
These rotary encoders are describedin the Encoders for Servo Drivesbrochure.Incremental TTL 1 VPPERN 1023–500 to 8192 lines3 signals for block commutation––ERN 1123–500 to 8192 lines3 signals for block commutationERN 13211024 to 4096 linesERN 13261)1024 to 4096 lines3 TTL signals for block commutation2)ERN 1381512 to 4096 linesERN 13872)2048 linesZ1 track for sine commutationERN 421ERN 4871024 to 4096 lines2048 linesZ1 track for sine commutation9
Rotary iemensEnDat–EBI 1135EQI 1131Positions/rev: 18 bits65 536 revolutions(buffer battery backup)EnDat 2.2/22Positions/rev: 19 bits4096 revolutionsEnDat 2.2/22Available withFunctional safetyWithout integral bearingECI/EQI/EBI 1100 seriesECI 1118ECI 1119Positions/rev: 18 bitsEnDat 2.2/22Positions/rev: 19 bitsEnDat 2.2/22Available withFunctional safety13 with ECI/EBIECI/EQI 1300 series–ECI 1319––Positions/rev: 19 bitsEnDat 2.2/01ECI/EQI 1300 seriesECI 1319––Positions/rev: 19 bitsEnDat 2.2/22Available withFunctional safetyECI/EBI 100 seriesECI 119EQI 1331Positions/rev: 19 bits4096 revolutionsEnDat 2.2/01EQI 1331–Positions/rev: 19 bits4096 revolutionsEnDat 2.2/22Available withFunctional safety––Positions/rev: 19 bitsEnDat 2.2/22 orEnDat 2.1/01EBI 135–Positions/rev: 19 bits65 536 revolutions(buffer battery backup)EnDat 2.2/22D: 30/38/50 mmECI/EBI 4000 seriesECI 4010ECI 4090SEBI 4010Positions/rev: 20 bitsEnDat 2.2/22Positions/rev: 20 bitsDRIVE-CLiQPositions/rev: 20 bits65 536 revolutions(buffer battery backup)EnDat 2.2/22––D: 90/180 mmERO 1400 series1)––Up to 37 500 signal periods through integrated 5/10/20/25-fold interpolationDRIVE-CLiQ is a registered trademark of SIEMENS AG.10–
These rotary encoders are describedin the Encoders for Servo Drivesbrochure.Incremental TTL 1 VPP––––––––ERO 1420ERO 1480512 to 1024 lines512 to 1024 linesERO 14701)1000/1500 lines11
Rotary encoders for special applicationsRotary encodersAbsoluteSingleturnInterface EnDatMultiturn 4096 revolutionsSSIEnDatSSIFor potentially explosive atmospheres in zones 1, 2, 21 and 22ECN/EQN/ERN 400 seriesECN 413ECN 413EQN 425EQN 425Positions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsPositions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsROC 413ROC 413ROQ 425ROQ 425Positions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsPositions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsROC 413ROC 413ROQ 425ROQ 425Positions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsPositions/rev: 13 bitsEnDat 2.2/01Positions/rev: 13 bitsROD 600––––ROD 1930––––––ROC/ROQ/ROD 400 seriesWith synchro flangeROC/ROQ/ROD 400 seriesWith clamping flange199 15For high bearing loads15018160For Siemens asynchronous motorsERN 401 series––EQN/ERN 400 series––EQN 425EQN 425Positions/rev: 13 bitsEnDat 2.1/01Positions/rev: 13 bits––Electronic handwheelHR 112012––
You will find these rotary encoders in theProduct OverviewRotary Encoders for Potentially ExplosiveAtmospheresIncremental TTL HTL 1 VPPERN 420ERN 430ERN 4801000 to 5000 lines1000 to 5000 lines1000 to 5000 linesROD 426ROD 436ROD 4861000 to 5000 lines1000 to 5000 lines1000 to 5000 linesROD 420ROD 430ROD 4801000 to 5000 lines1000 to 5000 lines1000 to 5000 linesROD 620ROD 630512 to 5000 lines512 to 5000 lines–ROD 193080–600 to 2400 lines828tary encoders are describibed iin theThese rotarydescribedSer Drives brochure.Encoders for ServoERN 421ERN 4311024 Lines1024 LinesERN 420ERN 4301024 Lines1024 LinesHR 1120–100 lines–––8413
MeasuringprinciplesMeasurement procedureMeasuring standardsHEIDENHAIN encoders with opticalscanning incorporate measuring standardsof periodic structures known asgraduations. These graduations are appliedto a carrier substrate of glass or steel.These precision graduations aremanufactured in various photolithographicprocesses. Graduations are produced from extremely hard chromium lines on glass matte-etched lines on gold-plated steeltape three-dimensional structures on glass orsteel substratesWith the absolute measuring method,the position value is available from theencoder immediately upon switch-onand can be called at any time by thesubsequent electronics. There is no needto move the axes to find the referenceposition. The absolute position informationis read from the graduated disk, which isformed from a serial absolute codestructure.A separate incremental track is interpolatedfor the position value and is simultaneouslyused to generate an optional incrementalsignal.Singleturn rotary encoders repeat theabsolute position information with eachrevolution. Multiturn encoders can alsodistinguish between revolutions.The photolithographic manufacturingprocesses developed by HEIDENHAINproduce grating periods of typically 50 µmto 4 µm.These processes permit very fine gratingperiods and are characterized by a highdefinition and homogeneity of the lineedges. Together with the photoelectricscanning method, this high edge definitionis crucial for the high quality of the outputsignals.The master graduations are manufacturedby HEIDENHAIN on custom-built, highprecision dividing engines.Encoders using the inductive scanningprinciple work with graduation structuresmade of copper and nickel. The graduationis applied to a carrier material for printedcircuits.Circular graduations of absolute rotary encodersWith the incremental measuringmethod, the graduation consists of aperiodic grating structure. The positioninformation is obtained by counting theindividual increments (measuring steps)from some point of origin. Since anabsolute reference is required to ascertainpositions, the graduated disks are providedwith an additional track that bears areference mark.Circular graduations of incremental rotary encoders14The absolute position established by thereference mark is gated with exactly onemeasuring step.The reference mark must therefore bescanned to establish an absolute referenceor to find the last selected datum.
AccuracyScanning methodsPhotoelectric scanning principleMost HEIDENHAIN encoders operateusing the of photoelectricscanning. Photoelectric scanning of ameasuring standard is contact-free, and assuch, free of wear. This method detectseven very fine lines, no more than a fewmicrometers wide, and generates outputsignals with very small signal periods.The ECN, EQN, ERN and ROC, ROQ, RODrotary encoders use the imaging scanning .Put simply, the imaging scanning functions by means of projected-lightsignal generation: two graduations withequal grating periods—the circular scaleand the scanning reticle—are movedrelative to each other. The carrier materialof the scanning reticle is transparent. Thegraduation on the measuring standard canlikewise be applied to a transparentsurface, but also to a reflective surface.When parallel light passes through agrating, light and dark surfaces areprojected at a certain distance. An indexgrating with the same grating period islocated here. When the two graduationsmove in relation to each other, the incidentlight is modulated: if the gaps are aligned,light passes through. If the lines of onegrating coincide with the gaps of the other,no light passes through. Photovoltaic cellsconvert these variations in light intensityinto nearly sinusoidal electrical signals.Practical mounting tolerances for encoderswith the imaging principle areachieved with grating periods of 10 µm andlarger.The absolute rotary encoders withoptimized scanning have a single largephotosensor instead of a group ofindividual photoelements. Its structureshave the same width as that of themeasuring standard. This makes it possibleto do without the scanning reticle withmatching structure.Other scanning principlesECI/EBI/EQI and RIC/RIQ rotary encodersoperate according to the inductivemeasuring principle. Here, graduationstructures modulate a high-frequencysignal in its amplitude and phase. Theposition value is always formed bysampling the signals of all receiver coilsdistributed evenly around thecircumference.The accuracy of position measurement withrotary encoders is mainly determined by the directional deviation of the radialgrating the eccentricity of the graduated disk tothe bearing the radial runout of the bearing The error due to the connection with ashaft coupling—for rotary encoders withstator coupling, this error lies within thesystem accuracy The interpolation errors during furtherprocessing of the measuring signals inthe integrated or external interpolationand digitizing electronicsFor incremental rotary encoders with linecounts up to 5000:The maximum direction error at 20 Cambient temperature and with slowrotation (sampling frequency between1 kHz and 2 kHz) is within 18 mech. x 3600 [angular seconds]Line count zwhich equals 1 grating period.20In the case of ROD rotary encoders, the6000 to 10 000 signal periods perrevolution are formed by signal doubling.The line count is important for the systemaccuracy.For absolute rotary encoders, theaccuracy of the absolute position values isgiven in the specifications of the respectiveencoder.LED light sourceCondenser lensScanning reticleMeasuring standardPhotocellsFor absolute rotary encoders withcomplementary incremental signals, theaccuracy depends on the line count:Line count1651220482048Accuracy 480 angular seconds 60 angular seconds 20 angular seconds 10 angular seconds(ROC 425 with highaccuracy)The accuracy data are given with respectto the incremental measuring signals at20 C ambient temperature and with slowrotation.photovoltaiccells I90 andI270 not shownPhotoelectric scanning according to the imaging scanning principle15
Mechanical design types and mountingRotary encoders with stator couplingECN/EQN/ERN rotary encoders haveintegrated bearings and a mounted statorcoupling. The stator coupling compensatesradial runout and alignment errors withoutsignificantly reducing the accuracy. Therotary encoder shaft is directly connectedwith the shaft to be measured. Duringangular acceleration of the shaft, the statorcoupling must absorb only that torqueresulting from friction in the bearing. Thestator coupling permits axial motion of themeasured shaft:ECN/EQN/ERN 400:L 41 min. with D 25L 56 min. with D 38 1 mmECN/EQN/ERN 1000: 0.
1024 to 4096 lines ERN 1326 1024 to 4096 lines 1) 3 TTL signals for block commutation ERN 421 1024 to 4096 lines 512 to 4096 lines ERN 1387 2048 lines Z1 track for sine commutation ERN 487 2048 lines Z1 track for sine
Incremental rotary encoders with TTL or HTL compatible out-put signals Information on rotary encoders that are available as safety-relat-ed position encoders under the designation functional safety. For selection table see page 10 Rotary encoders for integration in motors For motors without separate
Hermle B300 (2x) 800 600 500 CNC Heidenhain TNC530, 5-axis Hermle C1200 U 1200 800 500 CNC Heidenhain TNC430, 5-axis Fehlmann Picomax 54 500 250 160 CNC Heidenhain TNC310, 3-axis Hermle C40 850 700 500 CNC Siemens 840D, 5-axis Hermle UWF 902 S 600 450 500 CNC Heidenhain TNC426, 4-axis Hermle C 800V 800 600 500 CNC Heidenhain TNC430, 3-axis
† Brochure: Interfaces of HEIDENHAIN Encoders PWT 100 The PWT 100 is a testing device for checking the function and adjustment of incremental and absolute HEIDENHAIN encoders. Thanks to its compact dimensions and robust design, the PWT 100 is ideal for mobile use. You can fi nd more information in the Product Information PWT 100. PWT 100 .
3) See Temperature measurement in motors in the Encoders for Servo Drives brochure 4) See General electrical information in the Interfaces of HEIDENHAIN Encoders brochure or at www.heidenhain.de 5) 10 Hz to 55 Hz, 4.9 mm constant peak to peak
PWM 20 Diagnostic Kit for HEIDENHAIN Encoders with EnDat 2.1, EnDat 2.2, DRIVE-CLiQ, Fanuc, Mitsubishi and SSI interfaces PWM 20 is the successor of IK 215 and is an adjusting and testing unit for checking encoders with EnDat 2.1, EnDat 2.2, DRIVE-CLiQ, Fanuc, Mitsubishi and SSI interfaces.
encoders with 1 VPP, EnDat 2.1, and EnDat 2.2 interfaces. The encoders must be connected to the encoder input using a 25-pin D-sub connector, since the EIB transmits the temperature value to the control as an analog value. HEIDENHAIN EIB 5000 sensor boxes Sensor boxes for temperature measurement of direct drive motors Reduced cabling
Rotary encoders from HEIDENHAIN use either optical or inductive scanning principles. . 20 mm, 25 mm, 30 mm, 38 mm, or 50 mm IP64 TTL HTL 1 VPP 1000 to 5000 – – . the PWM 21 phase angle
Rotary encoders for the elevator industry The demands on elevator technology have been growing steadily in recent years, calling for higher speeds, higher shafts, smaller footprints, and lower operating costs. Also crucial is optimal passenger comfort, requiring smooth starts, constant accelerations, gentle braking, and precise
