Balance Bot

DT04

Stephan Baranoff

Nicole Beck

Chris Hamrock

Stephanie Kosec

Dr. Sastry

Balance Bot

DT04

Stephan Baranoff

Nicole Beck

Chris Hamrock

Stephanie Kosec

Dr. Sastry

IntroductionIntroduction

The Statement of Need

RoboGames holds an annual competition called the Balancing Robot Race. This competition challenges participants to design a one or two wheeled robot that can maintain its balance without any external support, and be the quickest to complete a timed, predetermined obstacle course. This is a Remote Controlled robot. The Balancing must be autonomous, but the driving can be controlled by an R/C unit.

The Statement of Need

RoboGames holds an annual competition called the Balancing Robot Race. This competition challenges participants to design a one or two wheeled robot that can maintain its balance without any external support, and be the quickest to complete a timed, predetermined obstacle course. This is a Remote Controlled robot. The Balancing must be autonomous, but the driving can be controlled by an R/C unit.

IntroductionIntroduction

The Design Problem Definition 

The Design Goal

A two or one wheeled remote controlled robot that can maintain its balance without any external support.

Objectives

To complete the predetermined obstacle course in the shortest amount of time, while maintaining balance.

Constraints

The robot must be designed in such a way that its weight does not exceed 50lbs, its size does not exceed 3’x 3’x 3’. It cannot use an

internal or external combustion engine and cannot harm the environment or any other robots in the competition.

The Design Problem Definition 

The Design Goal

A two or one wheeled remote controlled robot that can maintain its balance without any external support.

Objectives

To complete the predetermined obstacle course in the shortest amount of time, while maintaining balance.

Constraints

The robot must be designed in such a way that its weight does not exceed 50lbs, its size does not exceed 3’x 3’x 3’. It cannot use an

internal or external combustion engine and cannot harm the environment or any other robots in the competition.

Design Requirements SpecificationDesign Requirements SpecificationMechanical• With zero inputs (no velocity or turning request, no external applied force) in steady state the robot shall:

– S1: Not vary more than 3 degrees from vertical– S2: Not drift more than 6 inches from the the original position

• From an initial condition of zero linear speed on a level surface, the robot shall:– S3: Be able to recover to 0 degrees, measured from vertical, starting at an angle of no more than 30 degrees,

measured from vertical.• On a smooth level surface, the robot shall:

– S4: Have a linear velocity of no less than 48 inches/s• From a lateral velocity of 48 inches/s, on a smooth level surface, given a step input request to zero speed, the robot

shall:– S5: Stop within 6 inches of the step input– S6: Not vary more than 5 degrees from vertical during the transient stopping period– S7: Not move in the opposite direction of the original forward motion by more than 6 inches from the location

where the zero input was received.• From a constant velocity state the robot shall:

– S8: Be able to climb and descend ramps having no more than a 20 degree incline with less than a 6 inch/s change in velocity.

• When transitioning between surfaces (coefficient of friction having a step change) at a constant velocity the robot shall:

– S9: Not exhibit a change in velocity of more than 6 inch/s.

Control• C1: The control systems for the robot will be implemented as discrete time-domain equations on a digital

computing and logic system.

Mechanical• With zero inputs (no velocity or turning request, no external applied force) in steady state the robot shall:

– S1: Not vary more than 3 degrees from vertical– S2: Not drift more than 6 inches from the the original position

• From an initial condition of zero linear speed on a level surface, the robot shall:– S3: Be able to recover to 0 degrees, measured from vertical, starting at an angle of no more than 30 degrees,

measured from vertical.• On a smooth level surface, the robot shall:

– S4: Have a linear velocity of no less than 48 inches/s• From a lateral velocity of 48 inches/s, on a smooth level surface, given a step input request to zero speed, the robot

shall:– S5: Stop within 6 inches of the step input– S6: Not vary more than 5 degrees from vertical during the transient stopping period– S7: Not move in the opposite direction of the original forward motion by more than 6 inches from the location

where the zero input was received.• From a constant velocity state the robot shall:

– S8: Be able to climb and descend ramps having no more than a 20 degree incline with less than a 6 inch/s change in velocity.

• When transitioning between surfaces (coefficient of friction having a step change) at a constant velocity the robot shall:

– S9: Not exhibit a change in velocity of more than 6 inch/s.

Control• C1: The control systems for the robot will be implemented as discrete time-domain equations on a digital

computing and logic system.

Electrical• EL1: The angular position sensor will be able to detect the angle of tilt of the robot within 1 degree of the actual angle.• EL2: The angular rate sensor will be able to detect the angular velocity of the robot relative to vertical within 0.1

degrees/s.• EL3: The processors and digital logic subsystems will be capable of executing the required control algorithms and

digital filter calculations at no less than 50 times the maximum bandwidth of the input to the filter.

Power• P1: The motor driver will be capable of operating at a supply voltage of no less than 24 volts DC and no more than 48

volts DC.• P2: The motor driver will be capable of supplying no less than 30 amps DC of peak current.• P3: The motor driver will be capable of supplying no less than 15 amps DC of continuous current.• P4: The motor will be able to supply maximum peak stall torque with an input current of no more than 30 amps DC.• P5: The motor will be able to supply maximum continuous power with an input current of no more than 15 amps DC.• P6: The motor and motor driver will be capable of handling transient loads of full peak current and produce the rated

peak stall torque of the motor in less than 100 ms.• P7: The energy storage system supplying the motors and drivers will be capable of operating at 1 CA of current load

for 1 hour.• P8: The energy storage system will be able to be recharged from 30% charge to 70% charge in under 4 hours.

Ergonomic• ER1: There will be 2 emergency stop buttons, one on the Balance Bot and one on the Remote Control• ER2: The Balance Bot will safely stop all operation in no more than 2 s of either of the emergency stop buttons being

pressed.

Economic• EC: The parts required to build a prototype of the Balance Bot will cost less than $625.00.

Electrical• EL1: The angular position sensor will be able to detect the angle of tilt of the robot within 1 degree of the actual angle.• EL2: The angular rate sensor will be able to detect the angular velocity of the robot relative to vertical within 0.1

degrees/s.• EL3: The processors and digital logic subsystems will be capable of executing the required control algorithms and

digital filter calculations at no less than 50 times the maximum bandwidth of the input to the filter.

Power• P1: The motor driver will be capable of operating at a supply voltage of no less than 24 volts DC and no more than 48

volts DC.• P2: The motor driver will be capable of supplying no less than 30 amps DC of peak current.• P3: The motor driver will be capable of supplying no less than 15 amps DC of continuous current.• P4: The motor will be able to supply maximum peak stall torque with an input current of no more than 30 amps DC.• P5: The motor will be able to supply maximum continuous power with an input current of no more than 15 amps DC.• P6: The motor and motor driver will be capable of handling transient loads of full peak current and produce the rated

peak stall torque of the motor in less than 100 ms.• P7: The energy storage system supplying the motors and drivers will be capable of operating at 1 CA of current load

for 1 hour.• P8: The energy storage system will be able to be recharged from 30% charge to 70% charge in under 4 hours.

Ergonomic• ER1: There will be 2 emergency stop buttons, one on the Balance Bot and one on the Remote Control• ER2: The Balance Bot will safely stop all operation in no more than 2 s of either of the emergency stop buttons being

pressed.

Economic• EC: The parts required to build a prototype of the Balance Bot will cost less than $625.00.

Design Requirements SpecificationDesign Requirements Specification

Engineering CalculationsEngineering Calculations

ElectricalElectrical

Engineering CalculationsEngineering Calculations

PowerPower

Engineering CalculationsEngineering Calculations

ControlControl

Engineering CalculationsEngineering Calculations

MechanicalMechanical

Engineering CalculationsEngineering Calculations

ErgonomicErgonomic

Engineering CalculationsEngineering Calculations

Economic:• SD $100/person• Honors Program $75/person

– 3 members in Honors Program• Total Budget: $625

Economic:• SD $100/person• Honors Program $75/person

– 3 members in Honors Program• Total Budget: $625

Accepted Technical DesignAccepted Technical Design

Hardware Theory of Operation

-describe how the major hardware design blocks go together

Hardware Theory of Operation

-describe how the major hardware design blocks go together

μController

MOSFET Driver Circuit

MOSFET Driver Circuit

H-BRIDGE H-BRIDGECurrent Sense

Resistor

Current Sense

Amplifier

Current Sense

Resistor

Current Sense

Amplifier

Left PM DC Gear Motor

Right PM DC Gear Motor

EncoderEncoder

Left Wheel

Right Wheel

Accelerometer

IR Sensor

IR Sensor

ESTOP Input

Driver Inputs

Wireless Transceiver

Non-volatile Memory

Battery

Gyroscope

Hardware Block DiagramHardware Block Diagram

DC/DC Converte

r

Battery Battery

Accepted Technical DesignAccepted Technical Design

Discuss the progression of the design from level 0 to level n+1• The hardware block diagram began with an microprocessor, a battery, a motor, wheels and a

transceiver. From there it was decided that two motors were needed to independently control the wheels. In order to control the motor, a motor control circuit would need to be designed for each motor. Part of the motor control includes an H-bridge which will allow the robot to move both forward and backward. The H-bridge will supply the current to the motor and in order to control the amount of current going to the motor, the current sense amplifiers and current sensor resistors were added to the design. Also, since the H-bridge is controlled by a PWM signal, the MOSFET driver circuits were added to amplify the signal. PMDC gear motors with a 10:1 gear ratio were chosen in order to develop enough torque to move the Balance Bot.  

• Once the method of movement of the robot was determined, the control of the movement needed to be determined. It was decided that sensors would be added to accomplish this task. An accelerometer, gyroscope, and infrared sensors were specifically chosen to send the Balance Bot’s position signals back to the microprocessor.

•  • In order to power the robot, separate batteries would be needed for the motors and the

microprocessor. To ensure that the microprocessor receives the correct input voltage, a DC/DC converter was added to the output of the battery to regulate it.

• From the transceiver we added the signals that would be sent to the microprocessor. These signals include the driver inputs and the ESTOP.

For debugging and error logging purposes, a non volatile memory was added. Lastly, in order to meet competition guidelines as well as for safety, we added an additional ESTOP to the Balance Bot.

Discuss the progression of the design from level 0 to level n+1• The hardware block diagram began with an microprocessor, a battery, a motor, wheels and a

transceiver. From there it was decided that two motors were needed to independently control the wheels. In order to control the motor, a motor control circuit would need to be designed for each motor. Part of the motor control includes an H-bridge which will allow the robot to move both forward and backward. The H-bridge will supply the current to the motor and in order to control the amount of current going to the motor, the current sense amplifiers and current sensor resistors were added to the design. Also, since the H-bridge is controlled by a PWM signal, the MOSFET driver circuits were added to amplify the signal. PMDC gear motors with a 10:1 gear ratio were chosen in order to develop enough torque to move the Balance Bot.  

• Once the method of movement of the robot was determined, the control of the movement needed to be determined. It was decided that sensors would be added to accomplish this task. An accelerometer, gyroscope, and infrared sensors were specifically chosen to send the Balance Bot’s position signals back to the microprocessor.

•  • In order to power the robot, separate batteries would be needed for the motors and the

microprocessor. To ensure that the microprocessor receives the correct input voltage, a DC/DC converter was added to the output of the battery to regulate it.

• From the transceiver we added the signals that would be sent to the microprocessor. These signals include the driver inputs and the ESTOP.

For debugging and error logging purposes, a non volatile memory was added. Lastly, in order to meet competition guidelines as well as for safety, we added an additional ESTOP to the Balance Bot.

Accepted Technical DesignAccepted Technical Design

Software Theory of Operation

-describe how the major software design blocks go together

Software Theory of Operation

-describe how the major software design blocks go together

Accepted Technical DesignAccepted Technical Design

Discuss the progression of the design from level 0 to level n+1• The first software block diagram developed included inputs from sensors, processing, and outputs

to actuators. This generic system expanded as the hardware system components and requirements were addressed. The first piece of software added was a simple motor control interface that would transform a torque number within the software into a useful output readable by a motor controller. Once the motor controller design was added to the parts to be designed, that block was changed to include the motor control algorithms and digital logic.

• Sensors were the next logical piece of hardware added to the system. The sensors needed to measure a variety of physical parameters identified as important for the Balance Bot, but the output format from the sensors was not yet known. Multiple sensors were deemed necessary so a fusion of sensors became necessary. This block is a discrete time filter of some kind that was added to the system to support multiple sensors.

• The output of each sensor is not yet known, which inspired the addition of a device driver block to the software. The output of sensors usually needs to be calibrated and adjusted in some format to calculate a physical value, velocity for example, from a sensor output, such as ADC counts. A calculation of physical value from raw value software block was added for each component after the device drivers.

• Between the input sensors and the output actuators is the compensator that calculates the next output based on current inputs. Feedback from motors was added to the system and signals were routed between blocks to improve data flow accuracy. Safety and watchdog functionality was added in order to support debugging of the software system. This allows for both data logging for anomalous event root cause analysis as well as model parameter fitting. At this point, the software block diagrams were deemed complete for this level of design.

Discuss the progression of the design from level 0 to level n+1• The first software block diagram developed included inputs from sensors, processing, and outputs

to actuators. This generic system expanded as the hardware system components and requirements were addressed. The first piece of software added was a simple motor control interface that would transform a torque number within the software into a useful output readable by a motor controller. Once the motor controller design was added to the parts to be designed, that block was changed to include the motor control algorithms and digital logic.

• Sensors were the next logical piece of hardware added to the system. The sensors needed to measure a variety of physical parameters identified as important for the Balance Bot, but the output format from the sensors was not yet known. Multiple sensors were deemed necessary so a fusion of sensors became necessary. This block is a discrete time filter of some kind that was added to the system to support multiple sensors.

• The output of each sensor is not yet known, which inspired the addition of a device driver block to the software. The output of sensors usually needs to be calibrated and adjusted in some format to calculate a physical value, velocity for example, from a sensor output, such as ADC counts. A calculation of physical value from raw value software block was added for each component after the device drivers.

• Between the input sensors and the output actuators is the compensator that calculates the next output based on current inputs. Feedback from motors was added to the system and signals were routed between blocks to improve data flow accuracy. Safety and watchdog functionality was added in order to support debugging of the software system. This allows for both data logging for anomalous event root cause analysis as well as model parameter fitting. At this point, the software block diagrams were deemed complete for this level of design.