Procedure to Setup a 3ɸ Linear Motor This is a guide to configure a 3ɸ linear motor using either analog or digital encoder feedback with an Elmo Gold Line drive. Topic: Instructional David G. Thomas December 23, 2015
Agenda 1. Connect to Elmo drive through EASII software 2. Define actuator and feedback system 3. Set limits 4. Characterize current loop 5. Calibrate feedback 1 6. Commutate motor 7. Characterize control loop 8. Deploy/Save parameters 1. Feedback calibration only applies to analog (sin/cos) feedback. Digital quadrature feedback does not require calibration.
Before You Begin This guide assumes all hardware is properly connected and installed. The user should understand all risks associated with operating this electromechanical system. Moving parts should be safely constrained and guarded to prevent accidental injury. All electrical connections and cabling should be properly grounded and shielded for both safety and signal integrity. The complete system installation should be compliant with local codes and regulations. Dover Motion does not assume any responsibility for damage, harm, or loss that may arise from using this document.
Open EASII Software Navigate to the Elmo Application Studio II icon, and open the program.
Configure System Select System Configuration once the program loads.
Create Workspace Right click on Workspace, and choose New Workspace.
Choose Workspace Select or create a directory to save the new workspace. This example uses a folder named myworkspace.
Add Drive Right click on Workspace, and choose Add Gold Drive.
Set Drive Communications The new drive should now be listed in your Workspace as Drive01. Select Drive01 with the cursor. Under Target Connection change the Connection Type to Direct Access USB.
Set Drive COM Port Elmo utilizes a USB to serial adapter and displays the USB connection as a virtual COM port. Under Target Connection change the Serial Port USB to the appropriate COM port. This example utilizes COM4.
Connect to Drive Right click on Drive01 and select Connect.
Online You should now see the items in Item Configuration fully populated, and the red X next to Drive01 should now be replaced by a red dot and green line. Online Offline
Drive Setup First, select Drive Setup and Motion (1). Next, select Expert Tuning (2). 2 1
Axis Configuration Select the first heading under Drive Expert Tuner Axis Configurations. Change Electro Mechanical Configuration to Linear Motor Linear Load. The motor picture should now resemble a linear motor. Confirm the following settings: Axis and Control Configuration Single Axis Feedback (Loop) Configuration Single Feedback Mode of Operation Position [UM = 5] The lower 3 checkboxes should not be checked.
Motor Settings Under Drive Expert Tuner select Motor Settings. The Motor Type should read Linear Brushless (3 Phase). The following parameters should be entered based on the motor s datasheet: Peak Current Continuous Stall Current Maximal Motor Speed Motor Magnetic Pitch
Motor Settings This example uses the MMG-150. Since the electrical current specifications on the MMG datasheet are listed as peak of sine, divide by 1.414 ( 2) to get the RMS values. Additionally, enter the Maximal Motor Speed and Motor Magnetic Pitch. Peak Current [Arms] 5.4 1.414 ~ 3.82 Continuous Stall Current [Arms] 1.8 1.414 ~ 1.27
Feedback Settings (Analog, sin/cos) Under Drive Expert Tuner select Feedback Settings. Change Feedback on Motor to Analog Sin/Cos, Port B.
Feedback Settings (Analog, sin/cos) Change Multiplication Factor (1) (interpolation factor) to a reasonable number (i.e. 12 or 14). Under Resolution, micron/cycle (2) should be set to 20. Note, if the resolution becomes too fine due to greater interpolation, this can limit maximum acceleration. For example, a Multiplication Factor of 14 on a 20um pitch scale yields a resolution of ~1.22nm. The largest number the Elmo can handle is ±2 31 (±2.15 billion). Therefore, the largest acceleration would be roughly 2.62 m s 2. This example uses 12 for the Multiplication Factor. 1 2
Feedback Settings (Digital, AquadB) Under Drive Expert Tuner select Feedback Settings. Change Feedback on Motor to Encoder Quad, Port B.
Feedback Settings (Digital, AquadB) Under Resolution, micron/count (1) should be set appropriately based on the interpolator hardware used. This example assumes a 100nm/count encoder. The Glitch Filter (2) should be set to approximately 10 times the highest speed expected: 10* 2m s 100nm = 200million cnt sec. The highest setting available is 7.5x10 7. 2 1
Display User Units Under Drive Expert Tuner select Display User Units. Change the Position Display Units and Velocity Display Units to Millimeters and Millimeters/sec respectively.
Current Limits Under Drive Expert Tuner select Current Limits. Since the numbers entered previously were RMS, Elmo multiplies by 1.414 to get the peak of sine. For this MMG-150 example, the Peak Current and Continuous Current should match the datasheet specifications. If the numbers look correct, do not change anything.
Motion Limits Under Drive Expert Tuner select Motion Limits and Modulo. For this example, set Stop Deceleration to 9000. This acceleration will bound all other acceleration values to within this range. In other words, if Stop Deceleration is set to 1000, normal acceleration cannot be set to greater than this value. Max Velocity Command should be 2000 from the earlier entry.
Protections Under Drive Expert Tuner select Protections. Before tuning, leave these values large. If they are too small, tuning could prove to be difficult.
Settling Window Under Drive Expert Tuner select Settling Window. This example, uses the default numbers. If you have application specific values, you may enter them here.
Inputs and Outputs Under Drive Expert Tuner select Inputs and Outputs. This example, does not change any of these settings. If limits are connected, this is where they are specified. Forward Direction designates an input as the forward or positive limit switch while Reverse Direction designates an input as the reverse or negative limit switch.
Identification of Current Loop Under Drive Expert Tuner select Current Identification. Change Current Level to 40%. Experiment Phases A, B, and, C should all be checked. MAKE SURE THE STAGE IS IN THE CENTER OF TRAVEL! Click Identify. You will then be notified the stage is about to move. Click OK.
Identification Complete There should now be 2 graphs, Plant Magnitude and Plant Phase, showing the performance of the current loop. Additionally, the impedance of each motor phase is displayed to the right. If there is a faulty electrical connection or coil, it is likely to be observed here. Check that the measured resistance and inductance match the motor specification.
Design of Current Loop Under Drive Expert Tuner select Current Design. Increase Bandwidth to 5000 Hz. Then click Design.
Design Complete Once the design is complete, a Nichols plot is displayed showing frequency as a function of magnitude and phase. The tuning gains for the current loop are also displayed to the right.
Verification of Current Loop Under Drive Expert Tuner select Current Verification - Time. Check that Experiment Type is set to Auto, and Excitation Type is set to Step. MAKE SURE THE STAGE IS IN THE CENTER OF TRAVEL! Click Verify. You will then be notified the stage is about to move. Click OK.
Verification of Current Loop The commanded versus the actual current will be displayed. For higher bandwidth systems, a 20 to 30% signal overshoot is expected. This design is acceptable. Click Stop to end the test. ~20%
Verification of Current Loop Lowering the Controller Integral from 810 to 700 will decrease the overshoot along with bandwidth. ~10%
Verification of Current Loop Verify phases B and C perform similarly to phase A by selecting the respective phases from Test in Phases and repeating the verification test.
Sensor Calibration (Analog, sin/cos only) SKIP TO COMMUTATION IF USING DIGITAL ENCODER! Under Drive Expert Tuner select Sensor Calibration. Calibration Mode should be set to Automatic. Current Level should be set to 100%. Choose reasonable values for Displacement and Velocity. In this example, 1.4 electrical cycles and 0.5 electrical cycles/second are chose by default for Displacement and Velocity, respectively. Remember from earlier, the electrical cycle is 25.4mm, and there are 20um per encoder cycle. The goal is to pass through enough encoder cycles at a reasonable speed to calibrate the encoder signal. In this case 25.4mm = 20um 1270 encoder cycles. This is plenty.
Sensor Calibration (Analog, sin/cos only) Click Calibrate (1). Then you will be prompted by 2 popup windows: the first to enable the motor (2), and the second (3) to begin the experiment. Click OK on both to proceed. 2 3 1
Sensor Calibration (Analog, sin/cos only) At the conclusion of the calibration, you should see a popup window (1) indicating success. Click OK. You should now see 2 graphs (2) displaying the sine and cosine signals. 1 2
Sensor Calibration (Analog, sin/cos only) MAKE SURE THE STAGE IS IN THE CENTER OF TRAVEL! Click Verify (1). Then you will again be prompted by 2 popup windows: the first to enable the motor (2), and the second (3) to begin the experiment. Click OK on both to proceed. 2 1 3
Sensor Calibration (Analog, sin/cos only) At the conclusion of the verification, you should see a popup window (1) indicating success. Click OK. You should now see the same 2 graphs (2) with an overlay of the verification data (green) over the calibration data. 1 2
Commutation Under Drive Expert Tuner select Commutation. Change the Auto-Phasing Method to Binary Search. Current Level, Displacement, and Velocity should remain the same.
Commutation MAKE SURE THE STAGE IS IN THE CENTER OF TRAVEL! Click Run Commutation (1). Then you will again be prompted by 2 popup windows: the first to enable the motor (2), and the second (3) to begin the experiment. Note the direction of the motor s motion. This will need to be defined as either negative or positive. Click OK on both windows to proceed. 2 1 3
Commutation After the motor moves, assign the direction as either negative or positive. In this example, the negative direction was selected.
Commutation At the conclusion of the experiment, you should see a popup window (1) indicating success. Click OK. You should now see 2 graphs versus time (2): Field Angle and Socket 1 Position. The data displayed in the bottom graph, Socket 1 Position, should be a straight line. If it is not straight (i.e. jerky) try decreasing Velocity or increasing Current Level if it is not already at 100%. 1 2
Identification of Velocity and Position MAKE SURE THE STAGE IS IN THE CENTER OF TRAVEL! Under Drive Expert Tuner select Velocity and Position Identification. In this example, Max Velocity Error and Max Position Error are both reduced to 25 (mm/sec and mm, respectively). During tuning, the following error (position and velocity) can become quite large, but it is kept smaller in this example as there are no limit switches. Excitation Signal Band should be set to Normal. Current Level is set to 100%. If the current level is set too small, the plant may be poorly characterized during the experiment. Click Identify (1) and then OK (2) when prompted to start motion. 2 1
Identification of Velocity and Position The stage will produce a series of tones as it is excited at increasing frequencies. Once the experiment is finished, 2 graphs (Bode plot) will be displayed. In this example, there are no concerning resonances or anti-resonances.
Identification of Velocity and Position To demonstrate the effect of too little Current Level, the experiment was performed at 5 different, equally spaced levels: 20, 40, 60, 80, and 100%. Below 60%, the plant characteristic begins to change. If not testing at 100%, it may be a good idea to test a higher and lower Current Level to confirm there is sufficient current applied during the experiment. As a rule of thumb, the plots should not change shape above a threshold current although they may shift slightly (up and down). 40% 20%
Design of Velocity and Position Under Drive Expert Tuner select Velocity and Position Design. The Objective should be set to PI Controller + LPF. For this example, Scheduling is Off. Click Design.
Design of Velocity and Position Once the design is complete, a Nichols plot is displayed showing frequency as a function of magnitude and phase. The tuning parameters are displayed to the right.
Scheduling of Velocity and Position Under Drive Expert Tuner select Velocity and Position Scheduling. This example does not cover scheduling.
Verification of Velocity and Position Under Drive Expert Tuner select Velocity and Position Verification - Time. To verify the tuning, a scope will be setup and triggered to capture position error as a function of time.
Verification of Velocity and Position Scope Setup At the top of the window, click the Recording tab (1). To setup the measurement, click Signals (2). 1 2
Verification of Velocity and Position Scope Setup The Signal Editor window should appear. From the Signals list, click the + to the left of Position (1). Under Position, select Position Error. Next, highlight Chart#1 (2). Then, press the Add Signal (blue arrow) button (3). Position Error should appear below Chart#1 (4). Click OK. 3 4 2 1
Verification of Velocity and Position Scope Setup Change Resolution to 100 usec/point and Record Time to 1.638 sec (1). Click Trigger (2). The Trigger Editor window should appear. Under Global, select Begin Motion (3). Then click OK. This will set the scope to begin gathering data right at the start of motion (after it is armed). 3 1 2
Verification of Velocity and Position Motion Setup Setup a point to point move by entering endpoints in the 2 boxes next to PTP Absolute (1). This example uses -25 and 25. Check the first Repetitive box (2). Set the Speed to 10 (3). Finally, click the Enable button (4). 4 2 1 3
Verification of Velocity and Position Make It Go Click Start at the top of the menu (1). This will arm the scope to wait for motion to begin. Click one of the arrows in the PTP Absolute profiler to begin motion (2). Depending on which arrow is selected, motion will proceed to the corresponding endpoint. 1 2
Verification of Velocity and Position Make It Go The Position Error should be displayed in Chart#1. If the tuning is sufficient, the motion should be smooth with an acceptable settling time. Press Stop (1) to halt motion. Try increasing the Speed to 100. Click Start again to arm the scope. As before, select an arrow in the PTP Absolute profiler to begin and capture motion. If the moves look satisfactory, click Stop and then click Disable (2). 2 1
Summary It is now time to save all of this great work. Under Drive Expert Tuner select Summary. There are 3 checkboxes: Save Parameters in Drive, Upload Parameters from Drive, and Save Design Plants. Make sure all 3 are checked (1). Then click Save (2). 1 2
Summary After clicking Save, the parameters and data will be saved and loaded as specified. The progress is updated in the status window (1). The drive setup is now complete. 1
Motion Single Axis (Optional) After Expert Tuning has been completed, select Motion Single Axis to control and monitor the stage.
Shutdown Once the drive is in a Disabled state (1), disconnect the drive by right clicking on Drive01 (2). The software may now be closed by clicking the close icon (X) in the top right hand corner of the application window. 1 2