Critical design review:
biped 2016
Ijya Karki (Project Manager)
Brandon Perez (Systems Engineer)
Alan Valles (Electronics Engineer)
Hector Martinez (Manufacturing Engineer)
Image created by Hector Martinez
PROJECT OBJECTIVES
The project objective is to design a 6th generation toy Biped robot that will statically walk using two feet with the goal of dynamic walking.
MISSION PROFILE
Biped shall compete, alongside other toys such as Goliath and Velociraptors, in an end of semester approximately hour long game: Save The Human. Biped should successfully walk, using Goliath’s live video feed as the field of view, from the opposite end of the room to the finish area without coming into contact with a Velociraptor. The Biped will maneuver through multiple obstacles by turning through walls, sensing color pads, balancing on six degrees inclines/declines, and stepping through uneven terrain placed on top of Linoleum floors.
THE DESIGN
Servos
3Dot + Shield + IMU
DC motors
Servos
Color Sensor
Rotary Encoder
PROJECT FEATURES
Servos at Ankles
PROJECT FEATURES
Balancing Weight
Arms
Enclosed Incline Balance
SYSTEM BLOCK DIAGRAM
3DOT BOARD INTERFACE
I2C GPIO EXPANDER INTERFACE MATRIX
CABLE TREE
Electronic Design
Power, a 7.4V LiPo Battery will be used with a TI LM1084 stepping down voltage to 5v at the ext+ connection on the 3dot board.
An IMU will be the MPU-6050 will be used due to the cost of the selected device. A socket is provided that the breakout board will plug into on our shield.
A rotary position sensor will be used with an ADC on the I2C bus will be used to read motor shaft positions.
Electronic Design
A TAOS TCS3472FN color Sensor will be used to read the color pads on the floor of the game arena. This additional pcb will allow us to detect if we step on a colorpad during the game. It connects via I2C and will be mounted inside the cavity on the underside of the foot.
Color Sensor Experiment
A color sensor experiment was run in order to determine the optimal distance of the color sensor. The optimal position was found to be a ¼ inch. The color sensor did work up to 4 inches away but the difference between color pad and control environment color was small. Much closer to the color sensor, the TCS3472 chip raw values where much harder to distinguish between red,blue,green.
Physical breadboard
The breadboard with all components on the i2C bus. The current color sensor has 5v logic so the logic level converter on the side will be used for further testing...
Schematic
Pcb layout
Surface mount
Manually routed
Solidwork
Features - Modified Theo Jansen
Features - Weight Distribution
Simulation
Animation
SOFTWARE BLOCK DIAGRAM
4 custom Commands
WALK (Direction, State, Steps)
TURN (Direction, Angle)
TurnOnLED (LED)
TiltBody (Angle)
CUSTOM COMMANDS
High Level Flow Chart
This is a flowchart of how the logic will work once the game has begun. The game begins once we start walking.
PseudoCode Snippet
This is C++ code structure of how the turn command will look...
VERIFYING & VALIDATING OUR REQUIREMENTS
We shall verify our design requirements with the collected data from experiments, measurements, and analytical computations.
-Use an amp-meter to measure current and determine power consumption -Use solidworks to determine center-of-mass of the system throughout its entire walking motion
We shall validate our design requirements with the use of visual inspection and demonstration to meet customer and stakeholder expectations.
- Have the Goliath follow the Biped over ramps and around obstacles - Have the Biped practice walking and turning on uneven terrains
REQUIREMENTS TO BE VALIDATED
Req. No. | “The Biped Shall” Statement | Verification Success Criteria | Verification Method | Results | Pass / Fail |
1 | Use a 3Dot Board embedded system. | All Arduino control software shall be compiled onto the 3Dot board. | Inspection |
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2 | Have a shield for the 3DOT board that will utilize the I2C interface. | All additional I/O devices such as the Biped’s sensors and electromechanical actuators shall be addressed through I2C. | Inspection |
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3 | Use DC motors to control its walking motion. | Both legs of the Biped shall be powered by DC motors. | Inspection |
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4 | Shall be able to walk on inclines of (+/-) 6.5 degrees. | Biped shall be able to walk on inclines and declines of (+/-) 6.5 degrees of slope. | Demonstration |
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5 | Shall be operated through Arxtrerra firmware via Bluetooth telemetry. | Control of the Biped shall be done on a Arxterra firmware on an Android device via Bluetooth telemetry. | Demonstration |
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6 | Shall be able to turn left and right. | The Biped shall be able to turn into any direction the user wants in order to navigate thought the playing arena. | Demonstration |
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7 | Shall use a portable energy source capable of supplying power for an hour. | The chosen battery for the system should keep to Biped operating for the entire duration of the game. | Demonstration |
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REQUIREMENTS TO BE VERIFIED
Req. No. | “The Biped Shall” Statement | Verification Success Criteria | Verification Method | Results | Pass / Fail |
1 | The system’s sensors and actuators shall interface through the 3Dot board. | The 3Dot board shall control our entire system and interface with every electronic device in the system structure. | Inspection |
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2 | All system software shall be compiled onto the 3Dot board. | System control software shall be compiled onto the 3Dot board and no other microcontroller may be used. | Demonstration |
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3 | Arxterra firmware files shall be included in our software package for the 3Dot board. | Arxterra files must be included onto our Arduino software package in order to communicate properly with the Arxterra App on Android software. | Test |
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4 | An I2C interface shall be used in order to address additional devices for our system. | Based on our design, our I2C will support I/O support for 2-4 servos, 2 Shaft Encoders, A Color Sensor, and an RGB LED | Inspection |
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5 | Two DC motors shall be used on our Biped to produce a walking motion. | Each motor will independently crank the shaft for each leg. Our dual motor gearbox allows for each motor to be independently controlled. | Inspection |
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6 | Shall use a shaft encoding system to help keep the leg movement system in sync with the weight shifting system. | Shaft encoders will provide data to our processors about the shaft position of the motor its measuring. This data is necessary to keep both motors in sync with each other as well as keeping the leg-movement system in sync with our center-of-mass shifting system. | Test |
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7 | Servos on each of the Biped’s feet shall be implemented to produce turning. | When instructed to turn, the Biped shall have one foot in the air while the other foot on the ground pivots the system into the direction the user has requested to turn. | Test |
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8 | Shall use a color sensor to detect floor pads in the playing arena. | The Biped shall detect some sort of pads on the arena floor in order to achiever temporary vulnerability to its opponent so we have chosen for it to detect color. | Test |
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9 | Shall use a RGB LED to display the color of the pad that the color sensor has detected. | The Biped shall display the pad color onto an RGB LED to show acknowledgement to the pad detection when walking over one. | Test |
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10 | Shall use a servo to shift the system’s center of mass over from foot-to-foot. | A single servo will be used to shift the center-of-mass from foot to foot when taking steps to walk. This servo must stay in full sync with the leg-movement motors. | Test |
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11 | Shall use accelerometer to detect when the Biped is on an incline or decline. | The accelerometer shall be used to provide data about the systems angular position with respect to the ground. | Test |
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12 | Shall use PID control method to keep the system balanced on inclines and declines. | Data collected from the accelerometer shall be used as an into to drive a proportional output in a PID control method. | Test |
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13 | Shall use a servo to shift the system’s center of mass when walking on inclined and declined surfaces. | A servo shall be used to shift the system’s center-of-mass to ensure system stability when walking on inclines and declines. | Test |
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Budget
Updated schedule
Progression:
Concern:
Critical Path
Modify by 9th
Test by 16th
Finish Assembly by the 27th
Summarizing schedule status
50% complete