Difference between revisions of "S21: UTAH"

Revision as of 05:19, 23 May 2021

UTAH: Unit Tested to Avoid Hazards

Abstract

UTAH abstract

Objectives & Introduction

Show list of your objectives. This section includes the high level details of your project. You can write about the various sensors or peripherals you used to get your project completed.

Team Members & Responsibilities

• Akash Vachhani Gitlab
  • Leader
  • Geographical Controller

• Jonathan Beard Gitlab
  • Android Application Developer
  • Communication Bridge Controller

• Ameer Ali
  • Master Controller

• Jonathan Tran Gitlab
  • Sensors Controller

• Amritpal Sidhu
  • Motor Controller

• Shreevats Gadhikar Gitlab'
  • Motor Controller

Schedule

Parts List & Cost

Printed Circuit Board

We started with a very basic design for our RC car on a breadboard. All the components were integrated on the breadboard for testing purposes.

Breadboard Wiring

We later had a PCB manufactured. In our design we minimized the use of surface mount components and additional passive components. We reused the CAN transceiver modules we all purchased and the only passive components on the board were the two 120Ω termination resistors needed at each end of the CAN bus. The remainder of the PCB used a combination of male and female pin headers to connect all components together. This design, plus a lot of thoroughness by Shreevats, made it so we only needed 1 revision.

PCB Schematic

Challenges

The wirings on the breadboard succeed on the first attempt but later when we kept adding the components as per the requirements the wiring became a complete mess and was entangling everywhere due to which the car could not navigate properly. Every time the car collided, the wires used to get disconnected. So reconnecting the wires and debugging the hardware every time after the collision was the main challenge. So we decided to go with PCB.

Printed Circuit Board

PCB

PCB Layout

To overcome all the challenges which were faced on the breadboard we designed the PCB on EasyEDA. EasyEDA allows the creation and editing of schematic diagrams, and also the creation and editing of printed circuit board layouts and, optionally, the manufacture of printed circuit boards. So we implemented the custom PCB using EasyEDA Software in which we implemented all the four controller connections. The four controllers included Master Controller, Geo Controller, Sensor Controller, and Motor Controller. The communication of these four controllers is done via a CAN bus. The GPS and Compass are connected to the Geo controller. The four Matbotix Ultrasonic sensors and the Bluetooth module are connected to the sensor controller board, while the LCD and LEDs are connected to Master Controller. RPM sensor, DC motor, and Servo motor are connected to Motor Controller. Also, all four CAN Transceiver are connected to their respective board.

//Not completed (To be added more)

Using the EasyEDA we designed a 2 layer PCB. The dimension of the PCB was 12.5" * 4.5". The four controllers were placed at the four corners of the PCB while the other components were placed at the center.

//Not completed (To be added more)

Power Management

The main power came from a 7.4v Lipo battery. This 7.4v from the battery was given to ECS. ESC gave a power output of 6V. This 6V was given to the Pololu voltage regulator. We used 5V Step-Up/Step-Down Voltage Regulator S9V11F5 for powering our four controllers and their respective components. The S9V11F5 helps in switching step-up/step-down regulator efficiently to produces 5V from input voltages between 2 V and 16 V. Its ability to convert both higher and lower input voltages makes it useful for applications where the power supply voltage can vary greatly, it's suitable for application where we use a battery. The Pololu is a very compact (0.3″ × 0.45″) module and also has a typical efficiency of over 90% and can supply a typical output current of up to 1.5 A when the input voltage is around 5 V.

Challenges:
1. Calculating the power requirement for each device.
2. Using only one battery was a challenge.
3. Splitting the power to 3.3V, 5V, 6V from one battery to different components.
4. Finding the pitch and dimensions of each component and placing them in the correct place and orientation.
5. Finding the correct power IC which can serve all the requirements.
6. Routing the wires on the PCB.

CAN Communication

<Talk about your message IDs or communication strategy, such as periodic transmission, MIA management etc.>

Our message IDs were chosen based upon an agreed priority scheme. We assigned high priority IDs to messages that controlled the movement of the car, followed by sensor and GEO messages, and lowest priority messages were for debug and status.

Debug and status messages were sent in the 1Hz, and a few in the 10Hz, callbacks. The sensor and driver boards send data at the fastest rate (20Hz), so receiving all messages is done at 20Hz as well.

Each board managed MIAs using the auto generated API. Each board received all messages in one function call, and the service MIA function would be executed if messages a board was expecting did not arrive. The increment and threshold values for MIA were in units of milliseconds, so it was easy to adjust threshold values if we wanted a MIA to occur earlier or later.

Hardware Design

<Show your CAN bus hardware design>

DBC File

DBC File Link

VERSION ""

NS_ :
	BA_
	BA_DEF_
	BA_DEF_DEF_
	BA_DEF_DEF_REL_
	BA_DEF_REL_
	BA_DEF_SGTYPE_
	BA_REL_
	BA_SGTYPE_
	BO_TX_BU_
	BU_BO_REL_
	BU_EV_REL_
	BU_SG_REL_
	CAT_
	CAT_DEF_
	CM_
	ENVVAR_DATA_
	EV_DATA_
	FILTER
	NS_DESC_
	SGTYPE_
	SGTYPE_VAL_
	SG_MUL_VAL_
	SIGTYPE_VALTYPE_
	SIG_GROUP_
	SIG_TYPE_REF_
	SIG_VALTYPE_
	VAL_
	VAL_TABLE_

BS_:

BU_: DBG DRIVER IO MOTOR SENSOR GEO


BO_ 100 BRIDGE_APP_COMMANDS: 1 SENSOR
 SG_ APP_COMMAND : 0|2@1+ (1,0) [0|0] "" GEO,DRIVER
 
BO_ 101 MOTOR_CHANGE_SPEED_AND_ANGLE_MSG: 2 DRIVER
 SG_ DC_MOTOR_DRIVE_SPEED_sig : 0|8@1+ (0.1,-10) [-10|10] "kph" MOTOR
 SG_ SERVO_STEER_ANGLE_sig : 8|8@1+ (1,-45) [-45|45] "degrees" MOTOR

BO_ 102 SENSOR_SONARS_ROUTINE: 5 SENSOR
 SG_ SENSOR_SONARS_left : 0|10@1+ (1,0) [0|0] "inch" DRIVER
 SG_ SENSOR_SONARS_right : 10|10@1+ (1,0) [0|0] "inch" DRIVER
 SG_ SENSOR_SONARS_middle : 20|10@1+ (1,0) [0|0] "inch" DRIVER
 SG_ SENSOR_SONARS_rear : 30|10@1+ (1,0) [0|0] "inch" DRIVER

BO_ 300 GPS_DESTINATION_LOCATION: 8 SENSOR
 SG_ DEST_LATITUDE : 0|32@1+ (0.000001,-90.000000) [-90|90] "Degrees" GEO
 SG_ DEST_LONGITUDE : 32|32@1+ (0.000001,-180.000000) [-180|180] "Degrees" GEO

BO_ 301 COMPASS_HEADING_DISTANCE: 6 GEO
 SG_ CURRENT_HEADING : 0|12@1+ (0.1,0) [0|359.9] "Degrees" DRIVER,SENSOR
 SG_ DESTINATION_HEADING: 12|12@1+ (0.1,0) [0|359.9] "Degrees" DRIVER,SENSOR
 SG_ DISTANCE : 24|17@1+ (0.01,0) [0|0] "Meters" DRIVER,SENSOR

BO_ 501 GPS_CURRENT_INFO: 8 GEO
 SG_ GPS_CURRENT_LAT : 0|32@1+ (0.000001,-90.000000) [-90|90] "degrees" DRIVER,SENSOR,MOTOR
 SG_ GPS_CURRENT_LONG : 32|32@1+ (0.000001,-180.000000) [-180|180] "degrees" DRIVER,SENSOR,MOTOR

BO_ 502 GPS_COMPASS_STATUS : 1 GEO
 SG_ COMPASS_LOCK_VALID: 0|1@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER, SENSOR
 SG_ GPS_LOCK_VALID : 1|1@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER,SENSOR,MOTOR

BO_ 503 GPS_CURRENT_DESTINATIONS_DATA: 8 GEO
 SG_ CURRENT_DEST_LATITUDE : 0|32@1+ (0.000001,-90.000000) [-90|90] "Degrees" DRIVER
 SG_ CURRENT_DEST_LONGITUDE : 32|32@1+ (0.000001,-180.000000) [-180|180] "Degrees" DRIVER

BO_ 504 RC_CAR_SPEED_READ_MSG: 2 MOTOR
  SG_ RC_CAR_SPEED_sig : 0|8@1+ (0.1,-10) [-10|10] "kph" DRIVER,SENSOR

BO_ 750 DBG_RAW_COMPASS_DATA: 4 GEO
  SG_ SIGNED_REGISTER_VAL_MAG_X : 0|16@1+ (1.0,0) [-2048|2047] "GAUSSIAN" DRIVER,SENSOR
  SG_ SIGNED_REGISTER_VAL_MAG_Y : 16|16@1+ (1.0,0) [-2048|2047] "GAUSSIAN" DRIVER,SENSOR

BO_ 751 DBG_CONFIRM_RECEIVED_DESTINATION: 8 GEO
 SG_ RECEIVED_DEST_LATITUDE : 0|32@1+ (0.000001,-90.000000) [-90|90] "Degrees" SENSOR
 SG_ RECEIVED_DEST_LONGITUDE : 32|32@1+ (0.000001,-180.000000) [-180|180] "Degrees" SENSOR

BO_ 775 DBG_GPS_COMPASS_LOCK_LED_CHECK: 1 GEO
 SG_ COMPASS_LED_STATUS: 0|1@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER, SENSOR, MOTOR
 SG_ GPS_LED_STATUS : 1|1@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER, SENSOR, MOTOR

BO_ 780 DBG_GEO_CAN_STATUS: 3 GEO
 SG_ DBG_CAN_INIT_STATUS: 0|1@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER, SENSOR, MOTOR
 SG_ DBG_CAN_RX_DROP_COUNT : 1|16@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER,SENSOR,MOTOR

BO_ 781 DBG_SENSOR_CAN_STATUS: 3 SENSOR
 SG_ DBG_CAN_INIT_STATUS: 0|1@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER, GEO, MOTOR
 SG_ DBG_CAN_RX_DROP_COUNT : 1|16@1+ (1,0) [0|0] "drops" DRIVER,GEO,MOTOR

BO_ 782 DBG_MOTOR_CAN_STATUS: 3 MOTOR
 SG_ DBG_CAN_INIT_STATUS: 0|1@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER, SENSOR, GEO
 SG_ DBG_CAN_RX_DROP_COUNT : 1|16@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER,SENSOR,GEO

BO_ 783 DBG_DRIVER_CAN_STATUS: 3 DRIVER
 SG_ DBG_CAN_INIT_STATUS: 0|1@1+ (1,0) [0|0] "TRUE_FALSE" GEO, SENSOR, MOTOR
 SG_ DBG_CAN_RX_DROP_COUNT : 1|16@1+ (1,0) [0|0] "TRUE_FALSE" GEO,SENSOR,MOTOR

BO_ 784 DBG_MOTOR_INFO_MSG: 4 MOTOR
  SG_ DBG_DC_MOTOR_CURRENT_PWM_sig: 0|8@1+ (0.1,0) [10|20] "duty percent" DRIVER
  SG_ DBG_SERVO_MOTOR_CURRENT_PWM_sig : 8|8@1+ (0.1,0) [10|20] "duty percent" DRIVER
  SG_ DBG_PID_OUTPUT_VALUE_sig : 16|8@1+ (0.1,0) [0|0] "kph" DRIVER
  SG_ DBG_MOTOR_SELF_TEST_sig : 24|1@1+ (1,0) [0|0] "TRUE_FALSE" DRIVER

BO_ 001 DRIVER_HEARTBEAT: 1 DRIVER
 SG_ DRIVER_HEARTBEAT_cmd : 0|8@1+ (1,0) [0|0] "" SENSOR,MOTOR

BO_ 002 SENSOR_HEARTBEAT: 1 SENSOR
 SG_ DRIVER_HEARTBEAT_cmd : 0|8@1+ (1,0) [0|0] "" SENSOR,MOTOR

BO_ 003 GEO_HEARTBEAT: 1 GEO
 SG_ DRIVER_HEARTBEAT_cmd : 0|8@1+ (1,0) [0|0] "" SENSOR,MOTOR

BO_ 004 MOTOR_HEARTBEAT_MSG: 1 MOTOR
  SG_ MOTOR_HEARTBEAT_sig : 0|8@1+ (1,0) [0|255] "pulse" DRIVER

CM_ BU_ DRIVER "The driver controller driving the car";
CM_ BU_ MOTOR "The motor controller of the car";
CM_ BU_ SENSOR "The sensor controller of the car";
CM_ BO_ 100 "Sync message used to synchronize the controllers";
CM_ SG_ 100 DRIVER_HEARTBEAT_cmd "Heartbeat command from the driver";

BA_DEF_ "BusType" STRING ;
BA_DEF_ BO_ "GenMsgCycleTime" INT 0 0;
BA_DEF_ SG_ "FieldType" STRING ;

BA_DEF_DEF_ "BusType" "CAN";
BA_DEF_DEF_ "FieldType" "";
BA_DEF_DEF_ "GenMsgCycleTime" 0;

BA_ "GenMsgCycleTime" BO_ 100 1000;
BA_ "GenMsgCycleTime" BO_ 200 50;
BA_ "FieldType" SG_ 100 DRIVER_HEARTBEAT_cmd "DRIVER_HEARTBEAT_cmd";

VAL_ 100 DRIVER_HEARTBEAT_cmd 2 "DRIVER_HEARTBEAT_cmd_REBOOT" 1 "DRIVER_HEARTBEAT_cmd_SYNC" 0 "DRIVER_HEARTBEAT_cmd_NOOP" ;

Sensor ECU

<Picture and link to Gitlab>

Hardware Design

Sensor Hardware Design

Software Design

<List the code modules that are being called periodically.>

Technical Challenges

< List of problems and their detailed resolutions>

Motor ECU

<Picture and link to Gitlab>

Hardware Design

Motor hardware Design

Motor Controller includes the controlling of the DC motor, Servo motor, Electronic speed control (ESC), and the wheel encoder. The job of the motor controller is both to steer and spin the wheels in order to move the RC car to the target destination. The DC motor, servo motor, and ESC(Traxxas ESC XL-05) were provided with the Traxxas RC car. The wheel encoder was purchased separately from Traxxas's website. The job of the DC motor is to control the spinning of the rear 2 wheels through the utilization of ESC and wheel encoder whereas the job of the servo motor is to control the steering of the front 2 wheels.

DC Motor and ESC

The DC motor and ESC were provided with RC car. The DC motor is controlled by the ESC using PWM signals which were provided by the motor controller board for forward, neutral, and reverse movements. The ESC is powered ON using a 7.4 LiPo battery. The ESC converts this 7.4V to 6V and provides input to DC Motor.

The car can be operated at 100Hz in the following 3 modes :
Sport Mode (100% Forward, 100% Brakes, 100% Reverse)
Racing Mode (100% Forward, 100% Brakes, No Reverse)
Training Mode (50% Forward, 100% Brakes, 50% Reverse)

The PWM frequency for our Traxxas ESC needed to be 100Hz. An idle (motor stopped) duty cycle is 15%. The full duty cycle range is [10%, 20%], where [10%, 15%) is the reverse range, and (15%, 20%] is the forward range. We ended up limiting the duty cycle range to [13%, 17%] since the RC car had more power than we needed.

Servo Motor

The PWM frequency for our Traxxas Servo motor also needed to be 100Hz. An idle (wheel's pointing forward) duty cycle is 15%. The full duty cycle range is [10%, 20%], where [10%, 15%) is the steer left range, and (15%, 20%] is the steer right.

Wheel Encoder

For speed sensing we purchased a Traxxas RPM sensor as it mounted nicely in the gear box. The RPM sensor works by mounting a magnet to the spur gear and a hall effect sensor fixed to the gear box. To get the revolutions per second we used Timer2 as an input capture.

Software Design

The motor controller code modules consisted of 3 main parts, which are: 1. PWM drivers and motor logic, 2. RPM/speed sensor, 3. PID controller.

1. PWM drivers and motor logic

The PWM drivers were fairly easy to write since the SJ2 project provided an API for the low level function calls. Converting speed and angle values to duty cycle values was done by simply linearly mapping one onto the other. This worked fine for steering control, but due to varying grades the car needs to drive on, the PID is needed. The Traxxas ESC, as other students have discovered in the past, has safeguards to prevent damage to the motor by not allowing duty cycle to abruptly change from a forward signal to a reverse. The Traxxas transmitter uses a trigger for this, but as other students suggested, we used a state machine to transition into opposite directions. We found that going from reverse to forward simply requires stopping (15% duty cycle) the car first, while going from forward to reverse required sending the following signals: STOP, REVERSE, STOP, REVERSE. Since we did not consult with Traxxas, this logic was created through trial and error. Transitioning into the opposite direction might simply just require stopping first, and then delay until a speed is reached, then change directions. We had access to an oscilloscope, however we did not capture what actually happens to the DC motor duty cycle when the transmitter does the same transition.

We created a separate module that encapsulated the motor's drive logic, such as getting speed feedback to compute PID value, updating the DC motor's PWM in a state machine, and doing the start up self test. Another feature we incorporated was to have the motor controller listen for a message from the Bridge/App, so we could easily start and stop the car remotely. This feature was very helpful in testing.

2. RPM/speed sensor

To count the time interval between pulses the RPM sensor makes, we used one of the LPC's peripheral timers that allowed for an input capture feature. We configured the hardware registers such that a capture register is written the value of the timer count register when the input capture (pulse from RPM sensor) occurs. This required writing a low level API so that we could unit test the hardware reading and writing. An interrupt also triggers on a capture event to reset the timer counter, to make the value in the capture register easy to convert to revolutions per second. The circumference of the car's tire and spur gear ratio are needed to determine a scalar value to convert the revolutions per second to conventional speed units. Many students said the RPM sensor from Traxxas was inconsistent and unreliable for speed feedback. We thought that this might be because of how the sensor is measuring the speed of the spur gear and that the differential of the car might cause variation, however when the car goes in a straight line that should not be a problem. When we integration tested the software design with the PID using the above approach, the speed readings seemed stable enough for use with the PID.

3. PID controller

For situations where the DC motor needs to do more or less work (e.g. driving uphill or downhill) the linear mapping will not work. The proportional, integral, derivative (PID) controller is a widely used control mechanism to ensure a machine maintains a set point, and responds quickly and smoothly upon disturbances. In discrete time the integration becomes a summation and the derivative becomes a difference. The controller is based on an error from the set point, which is why the RPM sensor is needed to get feedback. The PID algorithm is fairly simple, as is tuning the gains. We found that the proportional and integral gains were enough to get the car to maintain speed.

Below is our design for the motor controller's periodic callbacks.

Technical Challenges

• Getting the state machine right for the DC motor to transition between forward and reverse, and vice versa, took some experimentation. Luckily other student's reports were available for us to get hints on what we needed to do.
• When first tuning the PID our boards were attached via jumper wires and breadboard on a piece of plexiglass. The plexiglass was not rigidly secured to the car either, which resulted in collisions with walls and wires becoming undone. All this led to more hardware issues and had us backtrack to get the PID tuned. Making sure the hardware is sound before doing full integration tests will save you time. This requires planning out the hardware early on, and preferably just getting a PCB manufactured.
• We were having problems during integration testing where the motors would not run. It's hard to say what the solution was for certain, but slowing down the rate we updated the PWMs (from 20Hz to 10Hz) seemed to be it.
• We damaged the ESC somehow and needed to purchase another. This cost us time and money. Make sure you don't accidentally short the ESC!
• Some unit tests were not written until after integration testing. This goes against test driven development, but due to deadlines we had to make a choice. Had we thought out the use cases of our modules and wrote unit tests sooner, I'm sure we would have avoided some in the field debugging.
• The code had to be redesigned for modularity and readability later on. Make sure to avoid software anti-patterns, like "blob," and use dependency injection to prevent tightly coupled code modules.

Geographical Controller

<Picture and link to Gitlab>

Hardware Design

Geo Hardware Design

Software Design

<List the code modules that are being called periodically.>

Technical Challenges

< List of problems and their detailed resolutions>

Communication Bridge Controller & LCD

<Picture and link to Gitlab>

Hardware Design

Software Design

<List the code modules that are being called periodically.>

Technical Challenges

< List of problems and their detailed resolutions>

Master Module

<Picture and link to Gitlab>

Hardware Design

Master controller Hardware Design

Software Design

<List the code modules that are being called periodically.>

Technical Challenges

< List of problems and their detailed resolutions>

Mobile Application

<Picture and link to Gitlab>

Hardware Design

Software Design

<List the code modules that are being called periodically.>

Technical Challenges

< List of problems and their detailed resolutions>

Conclusion

<Organized summary of the project>

<What did you learn?>

Project Video

Project Source Code

Advise for Future Students

<Bullet points and discussion>

Acknowledgement

References