Fall Biped 2016- Quantitative Values for our Requirements

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By: Brandon Perez
Approved by: Ijya Karki (Project Manager)

Table of Contents

Introduction

A final update of the requirements with completed values is provided below. The reason for preparing quantitative requirements is to ensure that during the validation and verification tests, we have more testable criteria.

Level 1 Requirements

The Biped shall statement…

  1. Shall be ready to participate in the game “Save the Human” on December 14th, 2016.

-Date has been determined for the semester duration and scheduling for class finals.

  1. Shall not exceed a cost of $125 to construct.

-Budget has been determined by the customer.

  1. Will use a 3Dot board, have a custom-built PCB, and utilize the I2C interface.

-These requirements have been set by the customer.

  1. Shall be able to walk a minimum speed of 0.32 mm/sec.

-Based on the expected arena size, we have estimated an expected worst case scenario   path of 45ft during the entire game duration. The red path on the picture below indicates an expected path for our Biped to travel which totals up to 23ft. We decided to double up the expected distance traveled due to a 100% uncertainty. With a 45ft distance to travel as a worst case scenario in a duration of an hour, we have set our minimum speed requirement to be 0.32 mm/sec because 45ft*(25.4mm/inch)*(12inches/ft)/(3600secs) = 0.32 mm/sec.

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  1. Shall be able to turn up to 180 degrees on each of its sides.

-The servos that have been provided to us have a 180-degree range of motion. We can restrict this range of motion even less, but we have decided to work with this full range because we will be able to turn 180 degrees from any side, which means our robot has the capability of turning directly around no matter what foot is placed on the ground.

  1. Shall be controlled in RC mode with custom commands on the Arxterra App up to 20ft away.

We are to control the Biped in RC mode during the game as it is a requirement by the customer. Since the longest dimension of the arena is 12ft, we would operate the Biped at 12ft away in the case we were right at the edge of the arena with the mobile device on the floor.

  1. Will have a mass less than or equal to 750 grams.

We were provided the servos to our group by the customer at no cost, therefore we conducted an experiment to see how much weight the servo could handle on top of its shaft’s axis while still being able to operate properly. The reason behind this type of load test instead of the traditional motor torque test was because these servos are being placed underneath the legs of the Biped to act as ankles to help turn the Biped. It was found the servos would still be able to turn loads up to approximately 750 grams which had defined our mass limit for our Biped.

  1. Shall be able to detect color pads in the arena of red, blue, and green color.

One of the requirements for the Biped to participate in the end-of-semester game, “Save the Human” is that the Biped must be able to detect “power-up” zones upon which the Biped can have vulnerability against the opponents. The power-up zones will be indicated by red, blue, and green color pads.

  1. Shall be able to operate for a minimum duration of an hour.

The Game Committee, which is the organization of Project managers for the groups participating in “Save the Human”, have decided that the game duration will possibly take up to an hour.

  1. Should be able to walk on inclines and decline having max angle deviations of (+/-)6.5 degrees.

The angle climb requirement along with the maximum angle deviations have been set by the Game Committee. This requirement has been dropped from a “shall” statement to a “should” due to lack of progress with achieving walking.

  1. Should be able to walk on uneven surface heights of 0.5 cm.

The height climb requirement has been a traditional requirement following from previous generations of Bipeds for capability of climbing over small heights. The max height deviation of 0.5cm has been set by the game committee.

Level 2 Requirements

The Biped shall statement…

  1. Will have a DC motor that can operate effectively at 5V and produce a torque of 9.75×10^-3 ft*lbs to effectively move the Biped’s legs.

The DC Motor we are to use must be rated at 5V to operate effectively with the 5V supply from the 3Dot’s DC Motor driver. A torque of 9.75×10^-3 ft*lbs has been determined because the Biped’s legs weigh 70 grams = 0.15 lbs each, and are cranked at 1 cm = 0.0325 ft from the DC motors axis. We used the formula T=F*d to obtain the minimum torque required of our motors.

  1. Will have a servo that can operate effectively at 5V and capable of horizontally moving a mass of 68g to effectively move the Biped’s arms.

The servos that will be used to control the Biped’s arms must be able to move the combined mass of the 3D printed arms over to both the left and right side of the Biped. They must have an operating voltage of 5V or greater because they are being powered through the external power source which will be supplying 5V with the use of an LDO regulator. The servos must be capable.

  1. Will use a rotary encoder to provide data regarding the shaft position at a rate of 40xMotor Speed to help effectively keep the leg-movement system in synchronous with the arm-raising system.

The rate of the rotary encoder has been chosen to be a ratio of 40:1 with respect to the motor speed to ensure an optimum resolution of the motor shaft position during operation that way the Biped can maintain stability when walking.

  1. Shall use an RGB LED to display the color of the color pads for a minute duration when walking over the “Power-Up” zones.

An RGB LED has been chosen to be an indicator for the user to know that the color sensor has detected the color of the color pads. When the Biped picks up the color of the power-up zone color pads using the color sensor, the resulting color shall be displayed on the RGB LED for a minute duration.

  1. Should use an IMU to detect incline levels and correct its center-of-mass when walking on inclines and declines of (+/-) 6.5 degrees.

An IMU has been chosen as our sensor or chose for detecting when the Biped is walking on inclines or declines of max angle deviations of (+/-)6.5 degrees which is the value that has been set by The Game Committee.

  1. Will use a battery capable of providing 560 mAh.

It was found that the amount of current drawn during our most energy expensive operation, walking, was 560mA. We decided to use this basis as our average current drawn from the battery. If our system must operate for a whole hour, then our battery must provide at least 560mAh because 560mA drawn for the course of an hour will have resulted in 560mAh of total energy consumed.

Conclusion

This is the final update to the requirements that will be used to come up with the verification and validation matrix. Once the matrix is completed, Biped can begin conducting tests as proof of our accomplishments.