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ITT Mirror Steering System Team P11565 Andrew Bishop Katie Hall Matt Manelis Ben Geiger Nurkanat Suttibayev Agenda Meeting Timeline Start Time 12:30 12:35 12:40 1:00 1:20 1:40 2:00 2:10 2:20 Topic of discussion Review Project Goals Review Customer needs Over all System Design Voice Coil Design Mechanical Mounting Design Control System Design Sensor and Feedback Design Power Regulator Design Wrap up Discussion Project Goals The mission of this project is to design and build a mirror steering system that can outperform commercially available systems in terms of Power Consumption. This project will provide appropriate documentation that can be utilized by future senior design teams for further refinement. Project Description The mirror steering system is a device that controls the angle of a mirror in two dimensions. This device is used in directing optical devices at the mirror and aiming the mirror at an object located a far distance away. The tilting of the mirror is achieved by the use of actuators, which push and pull the mirror into different locations. Project Appeal High Interaction between Mechanical and Electrical Designs which creates more design challenges The goal is to compete with and do better than commercially available designs The chance to work hands on with a design outside of our previous experiences. Customer Needs Importance Ranking: 9 – These needs have the highest importance and will be the main focus of the project 3 – These needs are somewhat important and will be the secondary focus of the project if time allows 1 – These needs are not as important as the rest of the needs and will only be focused on if the main and secondary needs have been satisfied Target Specs Importance Ranking: 9 – These needs have the highest importance and will be the main focus of the project 3 – These needs are somewhat important and will be the secondary focus of the project if time allows 1 – These needs are not as important as the rest of the needs and will only be focused on if the main and secondary needs have been satisfied System Design 2 Voice coils and 1 sensor Per Axis Flexure Spring Mounting PID Controller with VCCS Stage Underhung Voice Coil System Design (Section View) Mechanical System Model c1 Jӫ ө k c2 k F1 X(t) F1 L1 L2 L2 L1 Model for Axis 1 (ө-direction) y x Complete System Model PID controller to ensure system stability and settling time. The Trans-conductance (voltage converted to current) stage can be modeled as an attenuation. The voice coil is also modeled as a gain stage. PID controller is being tuned Voice Coil The basics of the voice coil is a device that uses current flow through a loop of wire and opposes a magnetic field to produce a force in single direction (positive or negative). It is the heart of the system and everything was based off of the force and dimensions of the Vc for a given input current. Voice Coil Continued The final design included 2 different voice coils, both with a 20mm outer diameter, one being 32mm tall, the other being about 22mm tall The 22mm tall VC has a higher magnetic field of .33T field in the gap area, the taller one having .38T field. Height not being too much of an issue for these gave us the choice to use the stronger field, and so giving more force for a given current. Mechanical Design Main assembly: - Waffle mirror (provided by ITT) attached to mirror mount by RTV adhesive - Flexure spring that allows system range of motion - Stem that connects the flexure to the top face of electronics box - Four actuators connected to mirror mount that will push and pull on mirror mount with generated force Relating Design to Needs/Specs Mirror Mount - CN8 (Size): The surface area of the mount is large enough to fit the flexure, voice coil contact point, and sensors, while not exceeding the diameter of the mirror - CN13 (Feasibility): The thickness is a standard value that can easily be purchased in stock (0.16’’) - ES3 (Modulus of Elasticity): Material must be stiff enough to withstand the forces and stresses imposed on part (6061 Aluminum) Finite Element Analysis To determine the displacement and stresses of the model, Finite Element Analysis is required SolidWorks/COSMOS software used for FEA Two types of analyses performed - Mirror and Flexure Structure - Electronics Box Mirror and Flexure FEA Setup To perform this analysis, the model is first constrained on the bottom face To simulate actuators acting in one axis, an upward force of 0.105 lbf is applied at one actuator, and a downward force of 0.105 lbf is applied at the other actuator To simulate actuators in two axes, two additional forces are added to the model at the other actuators Mirror and Flexure FEA Results One axis simulation - Displacement: 0.0587 in - Angle: 2.24º - Max Stress: 8350 psi - FOS: 4.78 von Mises Stress Displacement Factor of Safety Mirror and Flexure FEA Results Two axes simulation - Displacement: 0.0825 in - Angle: 3.15º - Max Stress: 10296 psi - FOS: 3.87 von Mises Stress Displacement Factor of Safety Electrical Box FEA Setup To perform this analysis, the model is first constrained on the bottom face The total weight of the components is summed, and applied on the top surface of the box Extra weight is added to simulate a worst case scenario (total force = 5lbs) Electrical Box FEA Results Results: - Displacement: 1.37e-5 in - Max Stress: 64.4 psi - FOS: 619 von Mises Stress Displacement Factor of Safety Determining Spring Constant To determine the spring constant of the flexure, varying forces were applied to the mount, and displacement was measured for each data set A graph was generated to show the Force and Displacement relationship The slope of the line is equal to the spring constant Simulated spring constant equal to 626.8 N/m, or 3.58 lbf/in Flexure Spring Design Modeled as seen on McMaster’s website Specific dimensions not given, so spring constant is not known Plan on purchasing part, and testing to determine kvalue, otherwise, machine our own part PID Controller 3 R7 C1 U2 2 1n 1k - V+ R10 5 1 + 1k 4 V- OP1177 C2 .1n U3 - V+ 1 + V- R11 5 1 110K OP1177 4 3 2 1k 2 5 4 V1 V+ + V- R5 R3 0 OP1177 U5 3 15Vdc R13 1k R9 .9k R4 2 - V+ 5 V- V_CMD 0 5 1 + 1k V- 4 4 R2 1k V_FB 10Vdc 1k R12 - V+ 1k V OP1177 0Vdc U4 2 1 + R1 10k 3 3 V U1 V2 15Vdc OP1177 R17 1k Voltage Controlled Current Source R21 R22 4k 2k 0 R23 100 R15 3 R14 10k R8 2 2 U6 1k - V+ 0 V- + 5 6 8 OPA547/BB V+ 4 10k Vo 1 (10.000,9.578) U87 4 3 E/S V- ILim - 5 1 + 12 OP177 4 V4 (10.000,145.345m) R_Iset 25 15Vdc 0 0 V5 15Vdc U7 3 -4 (10.000,-10.000) 2 5 V+ + V- -8 1 Theta X + 4 R18 10k OP177 -12 R19 I 25 0V V(U1:34) Theta X - 1 L1 420uH 2 1V V(U5:34) 2V -I(R19) 3V 4V 5V V_V_CMD 6V 7V 8V 9V 10V Sensor Design The sensor is based on the idea of a varying capacitance by using 2 metal plates close to each other One is stationary while the other moves with the mirror moves. As the plate moves the capacitance changes and changed the impedance of the circuit. An Impedance converter creates an equivalent resistance. A Wheatstone bridge circuit is used to find the variation of the impedance in terms of a voltage. The voltage VG Is then supplied back to the control circuitry to use as feedback. Sensor Design (cont.) Power Regulator 2 IN V1 OUT 3 V 1 DC = 24 AC = 6 TRAN = ADJ U3 LM317K C1 .1u R3 500 C2 100u 150mV R4 5.36k (362.611,141.542m) 100mV 0 U2 1 IN OUT 3 50mV V ADJ DC = -24 AC = 6 TRAN = 2 V2 LM337K C3 .1u R1 500 (1.6033K,6.0046m) C4 150u 0V 10mHz V(U3:OUT) R2 5.63k 100mHz V(U2:19) 1.0Hz 10Hz 100Hz Frequency 1.0KHz 10KHz 100KHz 1.0MHz Test Plan Pre-assembly and construction test plan: Makes sure that customer needs and engineering specs are met in pre-assembly stage Serves as a quality control procedure, in order to eliminate defects at early stage Mistake proofing Example: testing PCB, voice coil functionality, measuring important part dimensions. Final product test plan Shows if all the customer needs and specs met by final product Displays if there are functionality issues that needs to be eliminated prior delivery Examples: testing slew rate, settling time, power consumption, tilt range. Test Plan cont. Final Product Testing Tasks Engr. Spec. # Task (description) Unit of Measure Marginal Value ES4, ES5 Testing mirror settling time ms 60 ±5 ES6 Testing mirror speed (slew rate) rad/sec >50 ES8 Tilt range (max range of angle tilt can move) degrees 4.5 ±.5 N/A (QC purpose) Movement in X-axis NA NA N/A (QC purpose) Movement in Y-axis NA NA N/A (QC purpose) Movement in X and Y axis NA Na N/A (QC purpose) Movement flexibility (ability to draw geometrical shape) NA NA CN5, CN6 Testing steering accuracy/precision TBD TBD ES15 Testing Signal to noise ratio dB 96 ±25 ES1 Testing total power consumption of the system W <10 Comments/Status MSD II Project Plan Bill of Materials Note: Additional items will be added as necessary