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Mach-DSP User’s Manual

Document Number: MACH-DSP-9021

Page 54

www.ScannerMAX.com

7.5

Advanced control parameters

The controls that are found on the Advanced tab are separated into several categories,
including controls involved in position sensor scaling and fault detection, high frequency
velocity derivation, coil temperature calculation, and motor drive orientation. Normally
these controls only need to be used when scanners are being assembled along with a
Mach-DSP servo for the first time.

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Summary of Contents for Mach-DSP

Page 1: ...Mach DSP User s Manual Document Number MACH DSP 9021 Page 1 www ScannerMAX com Mach DSP Servo Driver and associated software Users Manual October 2020...

Page 2: ...ignal waveforms 6 2 Step waveforms 6 3 Raster waveforms 6 4 Vector waveforms 7 0 Mach DSP Servo Control Application program 7 1 Setting up communications 7 2 Menus toolbar status area and control para...

Page 3: ...essed and configured using a PC based Graphical User Interface software package where the built in Test Signal Generator Oscilloscope and Dynamic Signal Analyzer can be used to monitor and adjust the...

Page 4: ...on up to 18 bits for Command 17 bits Position Input Power Voltage 12V to 30 Volts DC version dependant Standard version requires 24V See Power Supply section for information Quiescent Current 200mA 23...

Page 5: ...Mach DSP User s Manual Document Number MACH DSP 9021 Page 5 www ScannerMAX com Mach DSP Package Dimensions millimeters...

Page 6: ...being mounted onto the projector chassis Note that all heat sink compounds include oil as a retaining element and this oil may evaporate over time Therefore if the Mach DSP will be used inside the sa...

Page 7: ...m 3 0 Connector locations and functions Please refer to the diagram below for an overall view of the location and function of each connector Note that each connector on the Mach DSP is unique thus hel...

Page 8: ...ecial ordered to operate optimally with power supply voltages as low as 12V or as high as 30V The actual power supply current requirements are dependent on the application and will vary as a function...

Page 9: ...2a Table 3 2a Analog Command Input Pin Function 1 X axis command input 2 Ground see below for details 3 X axis command input 4 Y axis command input 5 Ground see below for details 6 Y axis command inp...

Page 10: ...n the Analog Input connector It is very rare indeed that clients should make any connections to pins 2 and 5 of the Analog Input connector Again for all of the reasons why please read the book mention...

Page 11: ...and an optional Status feedback output The XY2 100 protocol uses separate inputs for X axis data and Y axis data The FB4 protocol uses a single input for both X and Y data and uses a single output fo...

Page 12: ...shown in the diagram above otherwise a Frame Sync Error will occur and data will not be communicated correctly In essence all of this means that the data is framed in 20 clock sequences The Clock line...

Page 13: ...16 bit position data a value of 0 all bits cleared normally represents the far left and far bottom of the scan field a value of 32768 represents the middle of the scan field and a value of 65535 all...

Page 14: ...lock and signals are observed by the Mach DSP on the high to low transitions of the clock Below is an oscilloscope screen shot showing the simplest implementation of the FB4 protocol Yellow is the clo...

Page 15: ...32 clocks X axis data is first with the MSB during clock number 1 Y axis data is next with MSB during clock number 17 FB4 Position return data The FB4 protocol uses one of the data lines to return the...

Page 16: ...position data are both communicated at the same time and on the same edges of the clock The screen shot above shows 100kHz sample rate which is reasonable for most applications To provide for synchron...

Page 17: ...terboard uses a 26 pin IDC connector which can be connected through a ribbon cable directly to a laser marking controller that also uses a 26 pin IDC connector Alternatively the ribbon cable can be te...

Page 18: ...or example these inputs may be used as an external SERVO ENABLE signal that will enable the servo driver when the laser Machine is ready for use but disable the servo driver and place it in standby ot...

Page 19: ...Specified Wire Size AWG 22 30 depending on pin type As expressed above the RXD and TXD signals use 3 3V signal levels These signals are protected by series resistors and Schottky diodes and therefore...

Page 20: ...tor drive current 1 V A 14 Y axis AGC drive voltage negative 15 NTC Thermistor 10K 3300 nominal 16 User defined analog output 4 17 User defined analog output 5 18 User defined analog output 6 Mating C...

Page 21: ...uts are updated at the sample rate that is used by the servo which is user adjustable between 100kHz and 300kHz with 160kHz being typical Albeit nearly all DACs experience some glitching between major...

Page 22: ...current instead of a positive current which is more common in the industry This is because most often the large body of an LED is the positive terminal and the small bond wire is driven with a negativ...

Page 23: ...uence that resets the integrator enables the servo loop and then gradually enables the command input and optionally indicating that the servo is ready using one or both user defined TTL outputs 4 2 Fu...

Page 24: ...the operation of the Mach DSP Faults are indicated by LED1 and LED2 flashing back and forth in a kind of railroad crossing manner The number of back and forth flashes will indicate the error number i...

Page 25: ...are also Class 2 servos that involve two separate integrators in the loop before the summing node but these are not used on galvanometer scanners Also note that just because a galvanometer servo drive...

Page 26: ...llows the integrator to force the mirror to its final target position but due to the low integrator gains used in this configuration the error integrator is only used for relatively low frequency and...

Page 27: ...osition resolution is 90 optical degrees 65 536 0 00138 degrees per bit 24 microradians The numbers above in microradians represent the best case resolution that is possible with any digital servo dri...

Page 28: ...Mach DSP User s Manual Document Number MACH DSP 9021 Page 28 www ScannerMAX com...

Page 29: ...Mach DSP User s Manual Document Number MACH DSP 9021 Page 29 www ScannerMAX com...

Page 30: ...r the adjustment of many different operational parameters However there are five primary gain controls that are most fundamental to servo tuning As described above the tunable parameters are Servo Gai...

Page 31: ...sition Proportional can serve to balance the Error Integrator and keep it from winding up This is particularly useful for PDF and PDFF servo configurations Low Frequency Damping Differentiated Positio...

Page 32: ...may each be enabled and adjusted to prevent oscillations from occurring in the servo loop Although the Mach DSP allows these filters to be configured as either low pass notch or phase lead a notch fi...

Page 33: ...ries small signal and large signal This terminology does not refer to the angular excursion of the mirror but rather to signal levels internal to the servo amplifier and particularly whether or not th...

Page 34: ...applications requiring settling to very small tolerances 200 microradians or less an over damped response frequently gives the fastest overall settling even though the rise time is slower because an...

Page 35: ...al raster command waveform is determined by taking the second integral of a square acceleration profile of a magnitude equal to the maximum unsaturated acceleration of the scan system The parameters o...

Page 36: ...marking and 3D printing where accurate tracking of complex waveforms is required It is frequently difficult to choose an optimization waveform for applications such as marking due to the complex non r...

Page 37: ...h DSP servo driver can be setup and adjusted using the Mach DSP Servo Control Application a program that runs on Windows based PCs Within the rest of this manual the Mach DSP Servo Control Application...

Page 38: ...ble will be recognized virtually instantly If you are using Windows XP you will need to obtain a driver from Pangolin In any event once the cable is plugged into the computer and the driver is install...

Page 39: ...k on the Port Settings tab and then click on the Advanced button which will display yet another window Locate the Latency Timer setting The default is 16 which is quite slow Set this to either 1 or 2...

Page 40: ...of their own With this being the case the COM port that is automatically chosen by the Mach DSP program will probably be the correct port Once the COM port is selected in the Mach DSP program you can...

Page 41: ...he scanners Expert mode is restricted to those customers who really need to be able to access and modify operational parameters Note that Pangolin does not publish how to go from User mode to Expert m...

Page 42: ...ime Status area left side of the Mach DSP program The entire left side of the Mach DSP program shows status information including information about the firmware loaded on the Mach DSP servo driver and...

Page 43: ...isabled by user controls or that it is not operational due to a problem such as a scanner not being plugged in a blown fuse or an electrical fault of some kind Power Supply Status When the colored blo...

Page 44: ...een exceeded in which case the servo will be shut down for several seconds before it is re started The temperature itself will also change color depending on the coil temperature Note that the estimat...

Page 45: ...expected to be used by intermediate level users These include Slew Rate Limiter parameters as well as some filter parameters The Advanced tab includes controls expected to be used only by the most adv...

Page 46: ...X com 7 3 Basic control parameters The controls that are found on the Basic tab are separated into three categories those controls that adjust Command Input those controls involved in Class 0 servo co...

Page 47: ...t versus motion this can be set to a negative number For example if this is set to 15 00 then an input command signal having 10V DC or a 16 bit signal having a value of 65535 will create 15 00 mechani...

Page 48: ...2 kHz High Frequency Damping Gain may not be needed at all in which case it can be left at zero In other cases both Low Frequency Damping Gain and High Frequency Damping Gain must be used normally no...

Page 49: ...about your application before adjusting this Enabling and Disabling the X axis or Y axis servo When Servo Gain Low Frequency Damping High Frequency Damping Error Integral and Position Proportional gai...

Page 50: ...t there are more controls in the Intermediate section than in any other section Because of this not all of the controls can be shown on the screen at the same time if the window is not resized and mad...

Page 51: ...the slew to accelerate either logarithmically if it is set to a positive number or linearly if it is set to a negative number based on input amplitude The ultimate benefit is the elimination of overs...

Page 52: ...ual position so that the Mach DSP provides true observed velocity Although this provides a very good estimate of velocity and one that does not contain noise this kind of velocity is normally not usab...

Page 53: ...he lowest impact on scanner position motion quality The filter frequency and filter Q are adjustable along with the filter type Generally the use of a lower Q allows for better control over resonances...

Page 54: ...e Advanced tab are separated into several categories including controls involved in position sensor scaling and fault detection high frequency velocity derivation coil temperature calculation and moto...

Page 55: ...o the position signal in order to make a zero volt command signal to correspond to the center of the projection surface This may be used to fine tune the zero position of the X Y system since it is di...

Page 56: ...ribed above Greater amounts of Torque constant to inertia ratio will allow lower amounts of High Frequency Damping gain When Observer gain is set to zero this control only influences the amount of Hig...

Page 57: ...especially true of the ScannerMAX Compact series of scanners as well as older moving iron galvanometers that used a torsion bar Other galvanometer scanners will not impose any torque on the rotor whe...

Page 58: ...ly exceeded The Mach DSP servo driver implements two modes in which the coil temperature may be calculated by the servo Mode 1 is to measure only the coil s RMS drive current and then estimate the tem...

Page 59: ...etting this to a value of 300 to 1000 is reasonable for ScannerMAX galvanometers Thermal resistance degrees C per watt When the X Y mount is a compression style mount that is supplied by Pangolin and...

Page 60: ...anometers require you to remove the mirrors from the scanners and orient the reflective surface of the mirror on the other side of the scanner shaft itself This is because other manufacturers of scann...

Page 61: ...Mach DSP influences the TTL Outputs The Mach DSP includes two optically isolated TTL Inputs and two optically isolated TTL Outputs found on the Status Control connector described in Table 3 3 of this...

Page 62: ...the source controlling device The Polarity control allows you to specify whether the Action described below is initiated as a result of the TTL Input being Active or Inactive Action The Action specifi...

Page 63: ...ity If X axis servo is Ready If Y axis servo is Ready If both X axis and Y axis servo are ready If either X axis or Y axis servo is ready If Power Amplifier is enabled If Servo board temperature is gr...

Page 64: ...for only a split second and then it goes back down to 59 degrees For safety reasons you might want the Mach DSP to continue to assert this condition for some number of seconds Dwell time takes on a mo...

Page 65: ...he machinery that is monitoring TTL Outputs may be fooled into believing that the scanning or system is in a safe state when it isn t And finally the TTL Output signals themselves are ultimately contr...

Page 66: ...re found on the Pangolin only tab only some of which are shown below and which may change from program version to version are used for fine tuning and calibrating the Mach DSP servo and are generally...

Page 67: ...lloscope and Analog Outputs These settings are all saved to flash memory on the Mach DSP amplifier using the Tuning menu as shown below Recalling and activating a tuning from memory Once a tuning is s...

Page 68: ...disk In addition to being able to save up to four separate tunings in memory all of the settings that make up a tuning can also be saved to a file on disk This allows you to have a virtually infinite...

Page 69: ...in the Tools menu in the Mach DSP program The tools are described below Each tool occupies its own window Multiple tool windows can be opened and these windows can be moved around on the screen and ma...

Page 70: ...al Generator drives the servo Test Signal Generator Settings are saved as part of the Scanner Tuning Note that the Test Signal Generator settings are stored with the scanner tuning so if you do not wa...

Page 71: ...ner tunings or at any other time when you d like to monitor the behavior inside and outside the Mach DSP servo loop The window used to access the Oscilloscope is also used to direct signals to the use...

Page 72: ...indow showing 50 microseconds per division in the picture above In addition to being able to specify the time per division the actual number of divisions can be selected using the scrollbar and zoom b...

Page 73: ...fer a separate vertical sensitivity for each channel Instead signals of like type are grouped together and a single sensitivity is offered for all signals in a particular group For example the Command...

Page 74: ...r is accessed using the Tools menu as shown below To use the Dynamic Signal Analyzer select an axis and test signal level and press Run Analysis The Dynamic Signal Analyzer will sweep a test signal fr...

Page 75: ...elps to eliminate overshoot when squarewaves or unstructured commands are used as an input The net result is similar to a Slew Rate Limiter but the Error Modifier can do this progressively thus helpin...

Page 76: ...y also consult the book LASER SCANNERS Technologies and Applications found at www LaserScanningBook com If you are unfamiliar with the process of tuning galvanometers it is recommended that you only a...

Page 77: ...nnected to the Mach DSP and indicate that there is a problem with the Position Sensor AGC of each scanner This is because no scanners are currently connected D On the Basic tab of the Mach DSP program...

Page 78: ...ease the Servo Gain up to 10 You should see something very similar to the screen shot above including the overshoot denoted by the blue arrow above If you do not see the overshoot continue to increase...

Page 79: ...ning toward the center of the projection surface L Continue to increase the Servo Gain and Low Frequency Damping little by little in a manner that you achieve a bit of overshoot with Servo Gain then e...

Page 80: ...rees per division The Error signal will be used to help you fine tune the controls to eliminate overshoots and also identify the step time that is being achieved by the system This is illustrated in t...

Page 81: ...on the scanners in the X Y mount such that they are projecting as closely as possible to the center of the projection surface It may be impossible to achieve a true center with simple mechanical adjus...

Page 82: ...instead of a sine wave Carefully watch for overshoots in the projected image and also on the Oscilloscope You will need to increase the Position Scale Factor setting in the Oscilloscope If you see any...

Page 83: ...application especially since removing this small error can come with its own complications and may hinder performance This section describes how the Position Error can be eliminated by adding an Integ...

Page 84: ...approximately 0 01 degrees or 175 microradians of error This error may be reduced by further increasing Error proportional Servo gain along with appropriate amounts of Low Frequency Damping and High...

Page 85: ...ccumulation by the integrator This large accumulated error becomes amplified by the servo ultimately causing an overshoot However this problem can be largely solved by adding an additional servo term...

Page 86: ...r trace shown above in green For a squarewave input ideally this should also be a squarewave essentially having flat tops If this is slanting upward or downward it shows that integration must be incre...

Page 87: ...t Signal Generator to produce waves greater than 18 degrees With this large squarewave input there is overshoot present This can be seen not only in the Position Error signal blue trace but also in th...

Page 88: ...g the anti windup gain the green trace can be made into a squarewave which is desirable Notice that there is still a small amount of overshoot present as indicated by the Position Error signal However...

Page 89: ...e step time approximately 350 microseconds However one of the tunings is more optimal achieving 40 faster step times The difference between the scanner tunings is how the Damping setting is used PD tu...

Page 90: ...g are also increased Notice that despite the Error Integral and Position Proportional gains being increased tremendously both of which contribute to acceleration in the same way as Servo Gain we still...

Page 91: ...n the previous two screen shots Also note that the position waveform now appears perfectly symmetrical in terms of time needed to accelerate and decelerate Comparing this to the screen shot above the...

Page 92: ...derivative feedback is an alternative to PID tuning Unlike PID where the Position Error is used to directly accelerate the mirror in the form of Servo gain PDF does not use Position Error at all Serv...

Page 93: ...al gain very slowly until pronounced overshoot is seen In this case we have increased Error Integral gain to only 5 K Increase Position proportional gain instead of Low Frequency Damping to largely el...

Page 94: ...ow Frequency Damping and Position proportional gain to increase servo bandwidth and decrease step time As was the case in step L of section 10 2 above eventually you will reach a point where the squar...

Page 95: ...a great deal of patience and skill and you will find that the controls work in non intuitive ways You will find that increasing Position proportional gain is useful in controlling the first overshoot...

Page 96: ...s are Lead 0 1 Mercury 0 1 Hexavalent Chromium 0 1 Polybrominated Biphenyls PBBs 0 1 Polybrominated Diphenyl Ethers PBDE 0 1 Cadmium 0 01 Bis 2 ethylhexyl phthalate DEHP 0 1 Dibutyl phthalate DBP 0 1...

Page 97: ...er 4 Object of the declaration Brand name ScannerMAX Model type Mach DSP 5 The object of the declaration described above is in conformity with the relevant Union harmonization legislation Electromagne...

Page 98: ...ty Patent Number 10 284 038 US Utility Patent Number 10 305 358 US Utility Patent Number 10 539 433 US Utility Patent Number 10 720 824 German Patent Utility Model Number 20 2012 009 275 8 German Pate...

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