Active Vibration Isolation Table

Transcription

1 Laboratory Tables Active Vibration Isolation Table TMCAmetek, Peabody, Massachusetts Page 1

2 Laboratory Tables Active Vibration Isolation Tables Introduction Feature highlights Compact Sub-Hertz Pendulum (CSP TM ) in each leg Precision Electronic Positioning System (PEPS ) PEPS-VX Vibration Cancellation System attached to PEPS. The table has been assembled at the factory. Leveling of the four CSP inserted in each leg and tuning of the PEPS/PEPS-VX controllers have been made and should provide satisfactory performance for a typical installation. Figure 1, 20 Series Active Vibration Isolation Table Air supply requirements The active vibration table requires a continuous supply of compressed air or Nitrogen to operate properly. For a complete discussion of the air supply requirements, see System Air Supply Requirements in the introduction section of this document. TMCAmetek, Peabody, Massachusetts Page 2

3 WARNINGS Power Supply The PEPS / PEPSVX controller does not use a universal power supply. Country voltage setting The power entry module must be configured for your country s voltage as follows. Remove the fuse access panel (Figure 10) on the PEPS controller. Remove the small voltage selection card from the module. Rotate the nylon tab to the correct voltage setting. Re-insert the card into the power entry module. Replace the cover. The nylon pin should protrude through a hole in the cover labeled with your country s voltage. Important The unit is rated for 100, 115, or 230 Volt operations. The 240 Volt setting should never be used. If you are in a country using 115 Volts, select the 120 Volt setting. Failure to properly configure the input power module can result in permanent damage to the unit. Power Cord Use only a UL/CSA/VDE marked mains power cord with the PEPS controller. The power cord should have at least 0.75mm2 wire (18 AWG), and include a PE ground. The cord should comply with all local, regional and national standards for the country where the system is to be used. Controller Usage The controller and its components are only to be used for its intended purposes described in this manual. Any other usage could jeopardize operator safety and cause possible injury. Pneumatic Isolators Great care should always be used when dealing with pneumatic isolators. Floating a payload on pneumatic isolators can generate many pinch points. One such pinch point is between the top of the fixed portion of the isolator, and the bottom of the load disk supporting the payload (see Figure 11). TMCAmetek, Peabody, Massachusetts Page 3

4 Installation and Setup Instructions Tools Required: 5/32 inch Allen key wrench Step 1 Install shelf on the frames lower tie bars. shelf Figure 2, Table shelf Step 2 Place PEPS/PEPS-VX controller on shelf. PEPS/PEPS-VX controller Figure 3, PEPS/PEPS Controller on shelf TMCAmetek, Peabody, Massachusetts Page 4

5 Step 3 Connect cables and tubing Connect the following from system harness to controller. 1/4 inch OD tubing as labeled. Connect five 1/4 inch OD tubing from pneumatic system. Proximity sensor connector Insert six pin green connector into green receptacle. Velocity sensor cables Connect BNC connector cables VS1, VS2 & VS3. Connect AC Power cord Ensure controller power switch is in the OFF position and connect AC power cord. Proximity Sensor Connector AC Power Switch 1/4 inch OD Tubing Figure 4, PEPS/PEPS Controller cable connections TMCAmetek, Peabody, Massachusetts Page 5

6 Proximity sensor mounted to isolator Isolator leg Velocity sensors mounted under tabletop Front Air supply Air regulator adjustment Waste Air 0utput Proximity sensor connector Velocity sensor Inputs VS1, VS2, VS3 Figure 5, PEPS/PEPS-VX Controller connections TMCAmetek, Peabody, Massachusetts Page 6

7 Step 4 Connect the air supply Connect air supply and set air supply and regulator pressure. Note For details regarding the air supply requirements, see System Air Supply Requirements in the introduction section of this document Air supply fittings: Tubing can be connected to a 1/4 or 1/8 inch NPT female fitting as shown in figure below. Air supply pressure psi ( kpa) Supply pressure or greater above the highest expected pressure in any isolator when the system is floating. Regulator Pressure 15 psi (100 kpa) or greater above the highest expected leg pressure. 40 psi is a typical regulator setting for floating the tabletop without a payload. When adding payload ensure pressure is increased to 15 psi above expected leg pressure. 1/4 inch tubing Approx. 30 feet long Air supply Adapter 1/4 NPT Male to 1/8 NPT Female Straight Connector 1/8 NPT Thread Adjust Regulator pressure Figure 6, Air Supply Connection TMCAmetek, Peabody, Massachusetts Page 7

8 Step 5 Center piston assembly Center each piston assembly on isolator top plate so that outside circumference of aluminum piston ring aligns with the edges of three small alignment holes spaced around piston ring 120 degrees apart. Piston assembly Alignment hole Isolator top plate Aluminum piston ring Alignment hole Top View Figure 7, Centering piston assembly TMCAmetek, Peabody, Massachusetts Page 8

9 Step 6 Place tabletop onto frame Place tabletop down onto frame so that top is centered over the four isolator legs without disturbing the centering of the piston assemblies. Piston assembly Figure 8, Mount tabletop Step 7 Attach velocity sensors Screw velocity sensors VC1, VC2 and VC3 into bottom of tabletop as shown in figure below. Connect BNC connector on end of sensor cable from system cable harness to base of sensor. VC2 VC3 VC1 Front view VC1 VC3 Front Sensor cables Figure 9, Attaching velocity sensors TMCAmetek, Peabody, Massachusetts Page 9

10 Vibration Isolation Systems Setup Guide, 2017 Step 8 /DERUDWRU\ 7DEOHV Float table top Turn the PEPS/PEPS-VX Controller s AC Power Switch ON. Reference figure 10 below. Expect to hear the sound of flowing air as the four isolators inflate lifting the tabletop. Once floating you should feel a spongy action on the tabletop over each of the isolator legs. ENGAGED (green LED) AIR INPUT from regulator AUX IN-OUT DB-25 connector WASTE AIR output Fuse panel and main voltage selection ZEROING ON/ ENGAGED (green LED) ISOLATOR 1 output to leg 1 AC Power ISOLATOR 2 output to leg 2 PROXIMITY SENSORS green input connector Out of Range adjust AC Power switch RANGE OK Out of Range/ (yellow/amber LED) ISOLATOR 3 & 4 output to legs 3 & 4 Clear plastic cover Figure 10, TMC Ametek, Peabody, Massachusetts PEPS/PEPS-VX Controller Page 10

11 Step 9 Adjust "level compensation screws Visual check Visually check piston level for each isolator leg to ensure piston is level with isolator top plate. Only adjust level compensation if required such as in figure below showing a slightly tilted piston. Caution: Keep fingers away from pinch point between top plate and aluminum ring. Leveling Screw-A Tilted piston and pendulum tube Leveling Screw-B Isolator top plate Isolator leg Figure 11, Centering piston assembly Adjustments Center piston assembly over leg by adjusting each screw as little as possible any one time. Continue to rotate around table slightly adjusting each leg until all have been optimized. Clockwise (cw) turn makes the piston assembly move away from the screw you are adjusting. Counter-clockwise (ccw) turn moves the piston assembly towards the screw. Move the payload parallel to the screws by adjusting screws equal amounts in opposite directions. Move the payload perpendicular to the line between the screws by adjusting screws in the same direction. Example: The figure above shows an isolator viewed from the side requiring a very sensitive adjustment of the pendulum's level. The pendulum tube is tilted 2.5 degrees. In this case, leveling screw-a should be adjusted a few turns clockwise, and leveling screw-b a few turns counterclockwise. TMCAmetek, Peabody, Massachusetts Page 11

12 Step 10 Add payload to tabletop Turn OFF air supply and AC power Place a typical payload onto the tabletop. Turn ON air supply and AC power to re-float system. Ensure tabletop is floating without any interference. Step 11 Check the following status LEDs RANGE OK OFF Good ON Gain settings need adjusting. ENGAGE Green LED ON Good ON/OFF Intermittent ON/OFF Gain settings need adjusting. (Ref. SMART ENABLE feature) Step 12 Excite tabletop with payload Manually excite tabletop using your hand and observe that tabletop has a quick impulse response and settle time. If any of the following conditions are observed then proceed to the section on Troubleshooting. Poor settle time Tabletop oscillates Erratic movements RANGE OK or ENGAGE LEDS indicate gain settings need adjusting. TMCAmetek, Peabody, Massachusetts Page 12

13 Troubleshooting Problem: My system doesn't float. Check power connection, fuse, and voltage setting. Check power 1) Set DIP switch #5 to ON (right position) ZEROING ON LED: ON indicates power is okay. 2) Set DIP switch #5 to OFF (left position) once power status is determined. Check for air flow: Ensure air supply is correctly connected. You can normally hear and feel air venting from the WASTE AIR output. (reference figure 10). Air supply pressure: Ensure supply pressure is at least 15psi (100kPa) above the highest isolator pressure. Test by increasing pressure. PEPS-VX Electronic gains: Increase each gain by 3 CW (clockwise) turns. Continue to increase each gain additional turns. Air lines: Ensure air lines are correctly connected, don t have any kinks or pinched restricting air flow. Problem: Some isolators fully inflate, while others get no air. Air lines: Ensure air lines are connected correctly, don t have any kinks or pinched restricting air flow. Proximity sensors: Ensure sensors are connected correctly, i.e. proximity sensors 1 and 2 are switched. Air supply pressure: Increase by 10psi (70kPa) Pitch & roll gains: increase either gain or both. TMCAmetek, Peabody, Massachusetts Page 13

14 Problem: After adding payload to the tabletop my system tilts back and forth from travel limit to travel limit (unstable in tilt). System may be gravitationally unstable by sitting on one edge for a while (up to several minutes), then suddenly `flop' over to the opposite edge. It will eventually flop back, and repeat the pattern. Any payload supported under its center-of-mass wants to `fall over'. The isolators provide a restoring force which resists this from happening. However, if the centerof-mass is too high or the distance between isolators too short, then the isolators will not be able to keep the payload upright. The general rule of thumb for stability is: W 2 (H m) > 1.5m W = center-to-center distance between the isolators H = height of the center-of-mass. Borderline systems tend to behave poorly. Some systems which are stable with mechanical height control valves may be unstable with PEPS. Mechanical valves act like springs which can help stabilize a system (but also degrade the vibration isolation). Removing the internal orifices also tends to make isolators softer, improving performance, but making the system less tilt stable. PEPS cannot make a mechanically unstable system stable. Solutions to this problem include the following: Lowering the center-of-gravity of the system Increasing the separation between the isolators Reconfiguring the system so the master/slave legs (legs 3\&4) are along the long edge of the payload Note TMC makes other types of isolators which may improve the situation, including smaller volume (stiffer) and fluid-damped MaxDamp isolators. Contact a TMC sales engineer for more information on this last option. Problem: I see some low-frequency noise in the positioning of the payload which is above the specification. Water trap Many air compressors cause water to accumulate in the air lines causing the servo valves in PEPS to work improperly. Your air supply system should have a water trap. Ensure that water trap isn t full. TMCAmetek, Peabody, Massachusetts Page 14

15 Barometric pressure Changes in barometric pressure can also cause noise on a payload since the sealed chambers of the isolators make them act like barometers. Barometric noise Many environments (such as clean rooms) have very aggressive air handling systems which can generate `barometric noise'. Likewise, if the system is placed near an air vent, or has some air circulating about it as part of a `mini environment', Positioning noise The table can see excess positioning noise. These sources of noise are not controllable by PEPS, and must be addressed at the source. The specification for PEPS was determined in a sealed room with no air circulation system running. Problem: The system takes too long to level after a disturbance (shift in mass distribution). Like mechanical valves, PEPS is a gain-limited servo. The gain is limited by the need to preserve vibration isolation in the system. For this reason, PEPS will level a payload at about the same speed as a mechanical valving system, depending on the disturbance. Pitch and roll gains Increase the pitch and roll gains until they are as high as they can be without the system oscillating. Though this does hurt the tilt vibration transfer, tilt noise is normally very low in most environments. Problem: My isolators inflate to full pressure lifting the payload to its travel limits, independent of the gain, or even if the power is off. If the isolators inflate when the power is off, you have probably connected the air supply tube from the system harness to the WASTE AIR port of the controller. Recheck the system plumbing. TMCAmetek, Peabody, Massachusetts Page 15

16 PEPS/PEPS-VX Controller Advance Setup Smart Enable The PEPS/PEPS-VX controller is a high-gain feedback system. To prevent the system from behaving badly when the velocity sensor feedback is turned on, it uses a smart enable feature. The controller monitors the proximity sensor signals. If the payload moves more than a few millimeters outside of its normal equilibrium position, the controller turns off the feedback. Once the payload moves back inside of its normal operating range, the controller will wait a few seconds, and then try to re-enable the velocity sensor feedback. The delay allows the system to stop moving, and prevents the system from engaging on accidental flybys. ENGAGED LED (reference figure 10) ON (green) = Indicates feedback is enabled. LED turns on when feedback is enabled and a several second time delay has passed. ALL DIP Switch (reference figure 10) ON (right position) normal operation, feedback is enabled and ENGAGED LED lights after several second delay. OFF (left position) diagnostic mode feedback is disabled Note When setting the gains in the following instructions, be aware of the smart enable function. Ensure the ENGAGED LED is ON when testing the impulse response. Too hard a push in testing may trigger the system to disable the feedback momentarily. DAMPING and ZEROING Gain and DIP Switch Settings Remove the clear plastic cover on the front panel (reference figure 10) for setting Damping and Zeroing DIP switches and adjusting the controller s gain settings. All DIP Switches are set to the OFF position for normal operation. Integrator Control: Switches 4 & 5 PEPS/PEPS-VX controller is a sophisticated feedback system which includes integration as part of its control algorithm. Any error in the position signals are integrated so the feedback to the valves will TMCAmetek, Peabody, Massachusetts Page 16

17 s continue to change until the error is driven to zero resulting in highly precise leveling capability. It is not always desirable, however, to have integration in a control loop. Under certain conditions, the integrators can saturate, and require a long time to recover. For this reason, the integrators can be configured to run in the following three modes: 1) Integrators ON After Float Normal mode of operation As tabletop starts to float integrators turn ON when proximity sensors detect a payload rise above a preset height. This mode prevents the integrators from saturating when the isolators are inflating during power-up. Switch 4 = OFF (left hand position) Switch 5 = OFF ENGAGED LED = ON, Integrators are engaged 2) Integrators Always ON Diagnostic mode Smart enable function is disabled. Integrators are always on forcing tabletop to float regardless of gain settings. Switch 4 = OFF Switch 5 = ON If the gains are set to low the system may have trouble floating. The system will take a very long time to come to equilibrium due to the saturation of the integrators caused during the initial isolator inflation. This mode is not recommended for a permanent configuration. 3) Integrators Always Off Diagnostic mode Setting enables adjusting proximity sensors on a system with very tight travel constraints in the isolators. It can sometimes be difficult to locate the operating height of the proximity sensors. When the integrators are OFF the system response is very fast. Set Integrators OFF Setting enables adjusting proximity sensors in their brackets to get the system floating within the mechanical constraints. Switch 4 = ON (integrators OFF) Switch 5 = OFF TMCAmetek, Peabody, Massachusetts Page 17

18 Set Integrators ON Set switch 4 to the OFF position. The float height may change a little, and final adjustments can be made to the sensors. Switch 4 = OFF (integrators ON) Switch 5 = OFF Power-Up Gain Adjustment The gain of the feedback loops determines the dynamic response of the isolation system. The following are two responses affected by the gain. Leveling time The time required for the payload to return to level after a disturbance. Level of Damping Determines how quickly the payload stops moving after an impulse response (also called ring down time). Monitoring gain adjustments Monitor the response of the payload using the proximity sensor outputs as follows. Connect oscilloscope to the three sensor outputs as follows. AUX IN-OUT, DB-25 Connector VC1... DB-25, pins 7 VC2... DB-25, pins 8 VC3... DB-25, pins 9 GND... DB-25, pins Set oscilloscope Vertical direction... v/div Horizontal direction s/div. Figure 12 below shows examples of the impulse response for different gain settings. Note TMC offers a breakout box to make connections to DB-25 connector easier for OEM customers. TMCAmetek, Peabody, Massachusetts Page 18

19 Setting Gains with Electronic Damping Every system is tested at the factory and the gains are set to values which will allow the system to float. Height Gain Adjustment Turn power ON. Connect an oscilloscope as follows. AUX IN-OUT, DB-25 Connector Height analog output... DB-25, pin 4 GND... DB-25, pins Press down lightly on the center of the payload, and you should see a response on the scope. Turn the gain down until the response looks like the left-hand curve in figure 12 below. Gradually increase the gain until the oscillatory behavior is suppressed (the right-hand curve below). Pitch and roll gain adjustment Repeat above procedure by moving the scope to the proper pin on the AUX IN-OUT, DB-25 connector each time. Excite the payload by pushing it sideways. Figure 12, Damping Too Low and at Optimum Do not set the gain any higher than is required to damp the motion. Figure 12 above shows what happens when the gains are increased too much. Notice that the pitch and roll degrees of freedom may not have as high a damping level as shown in Figure 13. If this is the case, then increase the gain until the damping of the primary oscillation stops improving. TMCAmetek, Peabody, Massachusetts Page 19

20 Figure 13, Gain Too High With Electronic Damping Figure 13 above shows what happens when the gain setting is set too high. The oscilloscope sensitivity has been increased to 100 mv/div. Notice that system has gone into a sustained oscillation at approximately 7.5Hz. Too Much Gain? TMCAmetek, Peabody, Massachusetts Page 20

21 Figure 14, Vibration Transfer and Impulse Responses for Different Gains TMCAmetek, Peabody, Massachusetts Page 21

22 RANGE OK LED The PEPS Go-No-Go Indicator TMCAmetek, Peabody, Massachusetts Page 22

23 Vibration Isolation Systems Setup Guide, 2017 /DERUDWRU\ 7DEOHV PEPS Technical Specifications Quoted technical specifications are typical values, and not a guaranteed performance level. They are subject to change without notice. Power Supply /115/230 VAC, 50/60 Hz, 20W max Fuse... T 0.25 A, 250 V slow-blow Power Cord... UL/CSA/VDE marked 0.75mm2 wire (18 AWG) w/pe ground Air Consumption... 45slpm (1.5 scfm) dry, clean air, filtered to 20μm or better Maximum Air Transfer Rate... 15slpm (0.5scfm) (Per isolator) Leveling Accuracy... 5μm height, 5 μradian pitch and roll Leveling Hysteresis (integrators on)... 5μm height, 5 μradian pitch and roll Leveling Hysteresis (integrators off)... 50μm height, 50 μradian pitch and roll Physical Dimensions mm (6.5 )H x 104mm (4.125 )W x 190mm (7.5 )D Weight (unit alone) Kg (5.52 lb) Standard Proximity Sensors... Turck Ni15-G30-Y0 NAMUR eddy-current sensors... (15mm operating height) Proximity Sensor gain... 2volts/mm Environmental For indoor use only, up to an elevation of... 2,000m (6560ft.) Temperature range... 5 C to 40 C Humidity range 80% up to 31 C, decreasing linearly to 50% relative humidity at 400 C Tolerance in mains supply voltage... +/-10% of nominal voltage Installation Category... II Pollution Degree... 2 AUX I/O, DB-25 Connector (colored ribbon cable) Pins 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) Pins Height Feed-Forward Input Roll Feed-Forward Input Pitch Feed-Forward Input Height Analog Output Roll Analog Output Pitch Analog Output Prox. Sensor (1) Output Prox. Sensor (2) Output Prox. Sensor (3) Output Out of Range Logic Out Out of Range Voltage TP +15 EXT. Power Input (750mA max.) -15 EXT. Power Input (100mA max.) 14) 15) 16) 17) 18) 19) 20) 21) 22) 23) 24) 25) Valve (1) Test Point Valve (2) Test Point Valve (3) Test Point GROUND GROUND GROUND GROUND GROUND GROUND GROUND GROUND EXT. Power Ground Figure 15, PEPS technical specification TMC Ametek, Peabody, Massachusetts Page 23

24 Vibration Isolation Systems Setup Guide, 2017 /DERUDWRU\ 7DEOHV PEPS-VX Technical Specifications Quoted technical specifications are typical values, and not a guaranteed performance level. They are subject to change without notice. Physical Dimensions (VX Controller)165mm (6.5 )H x 46mm (1.8 )W x 190mm (7.5 )D Physical Dimensions (w/peps) mm (6.5 )H x 153mm (6.0 )W x 190mm (7.5 )D Velocity Sensors... 90mm (3.53 )H x 44mm (1.7 ) Diameter geophones with... BNC connector & ¼ -20 Mounting Stud Weight (PEPS-VX Controller) Kg (3.02 lb) Leveling Accuracy... 20μm height, 20 μradian pitch and roll Leveling Hysteresis... 20μm height, 20 μradian pitch and roll Environmental For indoor use only, up to an elevation of... 2,000m (6560ft.) Temperature range... 5 C to 40 C Humidity range... 80% up to 31 C, decreasing linearly to... 50% relative humidity at 400 C Installation Category...II Pollution Degree... 2 AUX IN-OUT DB-25 connector (probe test point locations) and TO PEPS DB-25 connector (with colored ribbon cable) Pin 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) Pin Height Feed-Forward Input Roll Feed-Forward Input Pitch Feed-Forward Input Height Analog Output Roll Analog Output Pitch Analog Output Proximity Sensor (1) Output Proximity Sensor (2) Output Proximity Sensor (3) Output Out of Range Logic Out Out of Range Voltage TP +15 Ext. Power Input (750mA max.) -15 Ext. Power Input (100mA max.) 14) 15) 16) 17) 18) 19) 20) 21) 22) 23) 24) 25) Valve (1) Test Point Valve (2) Test Point Valve (3) Test Point Height Test Input Height Test Output Roll Test Input Roll Test Output Pitch Test Input Pitch Test Output GROUND GROUND EXT. Power Ground Figure 16, PEPS-VX technical specifications TMC Ametek, Peabody, Massachusetts Page 24

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