11/29/07 1 TCS November Presentation Telescope Control System (TCS) Modeling & Analysis Update Eric Warmbier

11/29/07 TCS November Presentation 2 Overview New engineer assigned to work on TCS3 project who needs to “come up to speed” First goal was to understand operation of TCS1 –TCS3 incorporates some of the TCS1 hardware –TCS1 is a fully operational system, which makes it a perfect example to study and start at Best method to accomplish this was to understand and modify original SIMULINK model Realistically, model will not be able to perfectly represent actual system Model provides general trends and a good understanding of the TCS and the telescope

11/29/07 TCS November Presentation 3 Documentation: Files & Format With no prior familiarity with the TCS, it was a great opportunity to create documentation for a future reader with no prior knowledge Documentation is contained in following documents each for TCS1 and TCS3 –“TCS Control Block Diagram” & “Model vs. Actual” Nontraditional, multipurpose format created in Visio Primarily technical in nature –“TCS Transfer Functions” Mathcad sheet containing derivations of transfer functions –“TCS Model” & “Original TCS Model” (multiple files) SIMULINK model (in PDF for presentation) –Revisions will be made on a continuous basis

11/29/07 TCS November Presentation 4 Model Creation Method The original SIMULINK model used as a basis Each block was then derived from the actual TCS schematics and compared with original Modifications were made where conflicts or missing blocks/components were found Only electrical, software, and motor blocks derived Mechanical model not analyzed in further detail –Created earlier with description and analysis by Tim Bond, see “TCS Servo System: Mechanical Modeling”, May 12, 2004

11/29/07 TCS November Presentation 5 Changes to Model Most calculations agreed with existing, original model blocks with the following exceptions: –Amplifier & Motor Motor transfer function in question Amplifier missing or simplification excluding it not intuitive No current output to monitor, making it difficult to compare against actual TCS system using available, measurable data –Feed forward pulses for offsets missing Important TCS1 feature that decreases settling time Functionally, pulses remove charge from integrator –Slew integrator short and feed forward missing Distinct mode with specific actions

11/29/07 TCS November Presentation 6 Model Results Model comparison with actual system is documented in “Model vs. Actual” Modification of the model is an ongoing process “Offset pulses” result in a faster settling time similar to the actual system (reduces overshoot) –The actual amount used in actual system isn’t known Slew mode is also similar to actual system Current levels do not correlate to the actual system –Model has higher currents, even on “drag” motor –Some additional, simple measurements will solve this Same axis tachometers appear to be too independent –Testing indicates tighter coupling

11/29/07 TCS November Presentation 7 Summary Understanding TCS hardware objective met TCS1 model is improved, but needs some additional modification after measurements –Comparison vs. actual required TCS3 model will be finished once TCS1 model is improved and verified within reasonable limits –TCS3 uses a significant portion of TCS1 Emphasis shifting away from models and more to working with what is present in system using models for trends where applicable

11/29/07 TCS November Presentation 8 Recommendations/Comments Do not spend significant amounts of time improving model –Goal of understanding system hardware met –Current testing at summit on TCS3 is yielding very positive results Model is worthwhile updating further as time allows because it does provide a simulation that gives insight into the system and general responses to changes