1. Active Suspension System
Students: Caleb Dell, Leslie Garcia, Alex Jaeger
Advisors: Prof. S. D. Gutschlag, Prof. Jing Wang
Who talks when
Leslie 2-11
Alex
Caleb - 23-end(37)

2. Outline Project Summary Previous Work System Block-Diagram
Component Descriptions
Work Completed
Future Work
References
Questions
In our presentation we will discussing..

3. Project Summary
Goal
Design a system to minimize vertical disturbance of a suspended body
Motivation
Provide a gentle ride to passengers by removing disturbances imparted to a vehicle due to uneven terrain
Apparatus Description:
3 Phase Induction Motor with VFD Control
Lower Platform
DC Voltage Linear Actuator
H-bridge
Microcontroller
Upper Platform
Position Sensor
Controllers:
Bang-Bang
Proportional
** More professional wording - break to two slides, increase size of font
Lower Platform: used to apply disturbance to the actuator and the upper platform
Upper platform: used to support applied load
Linear Actuator: Extends and retracts to reduce disturbance
Position sensor: upper platform sensor

4. Previous Work 1990-1991 Team Constructed basic apparatus
Used a pneumatic cylinder as the actuator mechanism
System was never functional
Disclaimer - This is with Linear actuator not a pneumatic

5. Previous Work: Team
Replaced pneumatic cylinder with an electric linear actuator
Developed a simplistic electromechanical simulink model for the linear actuator
System did not have safety features
Achieved rudimentary Proportional Controller
Simulink model is missing Tc and b, in addition to missing feedback components.

6. Previous Work: Team
Organized H-bridge and associated control electronics in an enclosure
Addressed Heat Dissipation
Added heat sinks and cooling fans
Safety and Emergency control
Limit switches
Emergency stop
with actuator brake
Safety shut-down
relays

7. Hardware Components Upper & Lower Platform
Position Sensor (Potentiometer)
Safety Relays
4 pole, double throw
Position Limit Switches
Linear Actuator
Motor Type: 160 volt brushed DC
Maximum Load Capacity: 3600 N (810 [lbs])
Rotating Camshaft driven by a 3-phase induction motor controlled by a Variable Frequency Drive (VFD)
Upper and lower Platform: The system will ensure that the upper platforms vertical motion will be maintained at the desired position specified by user. The lower platform will oscillate in the vertical direction and it will be controlled by the 3-phase AC induction motor connected to the camshaft.
Potentiometer:One is connected to the upper platform to measure instantaneous position and provide feedback to the controller.
Safety Relays: two 4 pole relays that are used for emergency system shut-down. In the default position the AC induction motor is open, so the camshaft will not rotate. Once a 24 volt DC signal is applied then the relay coil is active and the switches will close to disables the brake and connect the 3-phase VFD to the AC induction motor. Both the limit switches or emergency stop can switch the relay to the safety position.
Limit Switches: There are two limit switches connected to the system to guarantee an upper and lower bound of motion in the event of a controller malfunction. When one of the switches is activated then both safety relays will switch to their open positions and the system will stop working.
Linear Actuator: It will be driven by the H-bridge, which is also controlled by the Atmega128 board. The actuator is mounted to both the upper and lower platform. The actuator shaft will extend and retract to compensate for the lower platform movements based on the output of the potentiometer.
Rotating Camshaft: The rotating camshaft will rotate at all times during system operations unless the operator turns off the VFD controlling the 3-phase AC induction motor, or the emergency stop is activated.

8. Critical Electrical Hardware Components
LM317 Voltage Regulators (12[V]/1[A]) - Power for cooling fans
LM7815 Voltage Regulators (15[V]) - Vcc for H-bridge
LM7805 Voltage Regulator (5[V]) - Output side of the 6N137 optical isolator
MY2N-D2 Power Relays - Used as safety relays
6N137 Optical Isolator - protects microcontroller from inductive voltage spikes
MSK 4227 H-Bridge - controls linear actuator’s motor speed and direction
Maximum Current Rating 20 [A] at a case temperature of 25°C
Maximum Voltage Rating 200 [V]
Atmega128A Board (Embedded C)
Operating Voltages: [V]
Speed Grades: 0-16MHz
The white control box mounted to the top of the active suspension system contains the connections to all subsystems on the apparatus.
This includes an LM317 voltage regulator set to provide 12[V] for the cooling fans, one LM7815 voltage regulator used to provide 15[V] to the VCC pin for the MSK H-bridge, and one LM7805 voltage regulator used to provide 5[V] to the 6N137 optical isolators.
There are two OMRON MY2N-D2 safety relays connected to the emergency stop button which can be used to deactivate the linear actuator motor and the AC induction motor in an emergency.

9. System Block Diagram Position Input Position feedback
Active Suspension System Block Diagram
Inputs into the Active Suspension system:
Emergency stop, On/Off, User Input
After it goes into the active suspension system, a disturbance is added and then its feedback to be able to go through the system again, then we would get the actuator position

10. Work Completed Updated schematic diagram
Constructed and tested a discrete-component H-bridge
Corrected Three-phase motor safety relay connections
Designed and conducted experiments to determine the coulombic friction constant, Tc, the viscous friction constant, b, armature resistance, Ra, and inductance, La.
Developed accurate Simulink models for the linear actuator system
Created Bang-Bang Controller and Proportional Controller
Acquired simulated frequency responses
Incorporated a functional keypad to accept user input
Simulink models: gold standard, reduced controller that compensates tc and b, and a model that is based off of the frequency response plots

11. Discrete Component H-Bridge
Designed to emulate the MSK4227 H-bridge and ensured all team members understood the complex switching characteristics of the H-bridge used on the system
Used to test the linear actuator control software as it was developed to eliminate errors that could damage the MSK4227 H-bridge
Duty cycle must be less than 93% to ensure bootstrap capacitors recharge between switching cycles
Bootstrap capacitors provide a floating voltage for the high-side optical isolators to ensure the high-side power MOSFETs receive VGS = 15[V]
The floating voltage is required for the high-side optical isolators because the high- side MOSFET gate voltages must be VG = VDD +15[V] to adequately turn on the MOSFETs
Discrete component 93%
MSK 97%

12. Discrete Component H-bridge
Reverse

13. Three-Phase Motor Safety Relay
Team
Safety components were added
Three-phase was not functional
Used the updated schematic diagram to determine the wiring error
Three-phase induction motor was initially connected to the normally closed pins instead of the normally open pins
Three-phase motor - normally open

14. Modeling Friction Constants
Coulombic friction (Tc) and viscous damping coefficient (b) were not listed in the linear actuator datasheets
Experimental procedure to determine Tc and b
Generated software to drive the linear actuator at a specific shaft speed for a specified time
Measured average steady-state current flow to the actuator motor to compute generated torque
Computed steady-state linear velocity
Solved system of equations for Tc and b using ω and ω2
Not complex equations - simple

15. Simulink Diagram - Omega (ω)
Conditions:
45 volts
5 lbs
b = 1.94e-3
Tc = 0.285
*ADD PLOTS*
Get experimental plots
get simulink plots for position vs time - velocity

16. Steady-State Linear Velocity Using ω: Model vs. Experiment
Linear Velocity [in/s] vs time [s] (Simulink Model): Steady-state linear velocity of 4.996[in/sec] with 45[V] applied to the motor at 60% duty cycle and a 5[lb] supported load.
Linear Position Voltage [V] vs time [s] (Experimental): Steady-state linear position sensor voltage with 45[V] applied to the motor at 60% duty cycle and a 5[lb] supported load. Conversion yields a linear velocity of 4.8[in/sec]
This is what we are getting at the moment - W^2 should be more accurate

17. Simulink Diagram - ω2 Conditions: 45 volts 5 lbs b = 1.27e-5 Tc = 0.31
ADD IN SINE FUNCTION FOR B

18. Steady-State Linear Velocity Using ω2 : Model vs. Experiment
Linear Velocity [in/s] vs time [s] (Simulink Model): Steady-state linear velocity of 5.055[in/sec]
with 45[V] applied to the motor at 60% duty cycle and a 5[lb] supported load.
Linear Position Voltage [V] vs time [s] (Experimental): Steady-state linear position sensor voltage with 45[V] applied to the motor at 60% duty cycle and a 5[lb] supported load. Conversion yields a linear velocity of 4.8[in/sec]
Could be off 5% for the experimental data - ability to read experimental data is limited.
Difference between w and W^2 at low voltages should be virtually identical

19. Linear Actuator Simulink Model

20. Simulink Model Reduction
Second-Order
Transfer Function:
First-Order
Transfer Function:
ADD why can L be ignored? The time constant that correlates with the inductance is so small, it results in a break frequency that is beyond our operational limits of our system.
“-k-” is the force to torque constant.

21. Proportional Controller with Position Feedback
ADD why can L be ignored? The time constant that correlates with the inductance is so small, it results in a break frequency that is beyond our operational limits of our system.
“-k-” is the force to torque constant.

22. Testing the Microcontroller Subsystem
Microcontroller tasks:
Generate two Pulse-Width-Modulation (PWM) signals at varying duty cycles
Convert analog voltage signal from the upper platform position sensor potentiometer to its digital equivalent
Determine position based on converted analog signal
Alternate PWM signals for desired motor direction and speed to maintain the desired upper platform position based on controller output
Accept user input for desired platform position

23. Microcontroller - Pins Used
Output pins PB4 (OC0) and PB7 (OC2/OC1C) for generating two PWM signals to control the high-side transistors
Input pin PF0 (ADC0) for ADC input
Separately controlled output pins PE0 and PE1 to control the low-side transistors on the H-bridge
PORTA for LCD interfacing
PORTC for keypad interfacing
PORTD for keypad interrupts

24. Microcontroller - PWM Signal
Fast PWM mode
Pre-scalar = 64
Frequency = 976 [Hz]
OCR0 and OCR2 control duty cycle
figure - indicate where it is from,
Fix upper text boxes - bigger font
Where did 1Khz come from?
To be more efficient

25. Microcontroller - ADC Pin PF0 (ADC0) was used for the ADC input
The Atmega128A uses a built-in 10-bit ADC
The six inch upper platform displacement required using the default 0-5 [V] ADC input voltage range
The full six inch length of actuator stroke equated to a 5 [V] ADC input
The limit switches were used to limit the actuator stroke range from one to five inches to ensure the actuator did not abruptly reach the end of its stroke
ADC input is used to compute current position

26. Proposed Bang-Bang Controller Flow Diagram

27. Proportional Controller Flow Diagram

28. Atmega128 Keypad Functionality

29. Step Input Response - Kp = 5 Simulated Results Experimental Results

30. Step Input Response - Kp = 10 Simulated Results Experimental Results

31. Step Input Response - Kp = 15 Simulated Results Experimental Results

32. Frequency Response

33. Future Work
To further improve the apparatus, changes that can be made include:
Implementing a Proportional- Integrator (PI)
Implementing a Proportional-Integrator-Derivative (PID)
Replacing the potentiometer with an accelerometer [Inertial Measurement Unit (IMU)]

34. References
[1]   A. Serreurier, J. Rose, C. Ramseyer, R. Vassey (2017): 
[2] A. Tantos, “H-Bridges - The Basics.” Modular Circuits, [Online]. Available: secrets/h-bridges-the-basics/. [Accessed: Oct. 20, 2018]
[3]   Atmel, “8’bit Atmel Microcontroller with 128Kbytes In-System Programmable Flash,” ATmega128/L Datasheet, 2011
[4]   Avago, “2.5 Amp Output Current IGBT Gate Drive Optocoupler,” HCPL-3120/J312 datasheet, March 21, 2016
[5]   G. Franklin, D. Powell, and A. Emami-Naeini, Feedback Control of Dynamic Systems, Seventh. Pearson, 2015.
[6]   Industrial Devices Corp., “Electric Cylinder Overview,” EC2-H Series Datasheet
[7]   Maurey, “Linear Motion Potentiometers,” P1613 Datasheet
[8]   M. S. Kennedy Corp., “200 Volt 20 Amp MOSFET H-Bridge With Gate Drive,” MSK 4227 Datasheet, November  2004
[9]   Omron, “Miniature Power Relays,” MY4N-D2 Datasheet
[10] STMicrocontrollers, “N-Channel 250V – 22A Power MOSFET,” STP22NS25Z Datasheet
[11] Texas Instruments, “LM317 3-Terminal Adjustable Regulator,” LM317 Datasheet

35. Thank you Prof. Gutschlag and Dr. Wang!
Acknowledgements
Thank you Prof. Gutschlag and Dr. Wang!

36. Questions include back up slide for equations
bootstrap capacitor - explain it

37. Schematic Diagram

38. Forward Motion Simulation
Signal 1 (Top): 50% Duty cycle control signal applied to the HINA input by the microcontroller
Signal 2 (Center):Voltage at the gate of MOSFET T1
Signal 3 (Bottom): Voltage across the controlled permanent magnet Pittmann DC motor