Hybrid motor and test bench control system

Operation flow

1. B off, A and C open
2. if fuel tank is filled and pressure >= 750 psi, go to 3, else go to 1
3. C and A are off
4. wait for launch signal
5. D is activated to disconnect the fill line from the fuel tank
6. Igniter is ignited
7. Wait for a delay
8. F is open
9. Rocket is launched

Components

Processing units

The processing units chosen were the PIC32MZ2048.

The requirements for the motor control MCU are as follows:

• 1 SPI bus, for the SD card
• At least 6 GPIOs, probably a couple more to be safe
• 1 UART bus to send data to the launch pad
• Interrupt support on the UART bus if commands are to be received from the control station
• FATfs support
• at least 4KB of RAM
• 4 ADC
• (bus for the load cell)
• (GPIOs for the continuity test)

The requirements for the RF communication management MCU are as follows:

• 2 UART bus, 3 would be nice though
• Interrupt support on two UART ports, maybe needed on the third one if commands are to be received from the control station.
• Good error detection capabilities, CRC would be best

Sensors

Note: pressure sensors output an analog signal that has a range of 0 - Vref V. This means the maximum output value is equal to the Vdd of the sensor.

• P1: Used to measure the flow rate of the fuel to the combustion chamber
• P2: Used to measure the flow rate of the fuel to the combustion chamber
• P3: Pressure inside the fuel tank
• P4: Pressure inside the combustion chamber
• C1: Continuity test of the igniter
• F1: (test mode only) The load cell that measure the force of the motor during tests

Actuators

The motor control system control 6 actuators:

• A: First valve to control the filling of the fuel tank
• B: Purge valve for the fill line of the fuel tank
• C: Second valve to control the filling of the fuel tank
• D: Disconnect control of the fill line from the fuel tank
• E: Purge valve for the fuel tank
• F: Valve to control the fuel flow to the combustion chamber

Misc notes

• pistons that disconnect the fill line from the fuel tank must retain their state unless it is changed to avoid a change of state when the line is disconnected and signals don't pass anymore. However, that same piston should ideally not remain in the "disconnect" state too long
• the control of the pistons must be in the tower (fill line) because they are outside the rocket