Download It is the year 2115, and we have successfully discovered

It is the year 2115, and we have successfully discovered unobtanium and have begun mining operations
for extracting it. Being that it is very dangerous to humans to perform the mining operations;
autonomus mining carts are being developed to aid in the mining operations. You are responsible for
developing the initial mechanical / electrical interface designs with supporting analysis. To do this you
will need to develop the requirements for the motors as well as addressing the needs for a basic
electronics drive system.
State any assumptions and cite reference all material.
An initial sketch rendering of the mining cart known as an “Auto-hauler” is shown in figures 1a and 1b.
Figures 1a and 1b – Autohauler. The size of the robot is 3 feet wide (including wheels), and 6 feet long including wheels. It
uses 4 wheels in simple quad-steer for mobility. The wheels are 9” in radius, and 6” in width.
Vehicle Requirements.
The vehicle shall be able to travel at a top velocity 3feet/second, while carrying a load of unobtanium up
to 1000 lbs including the vehicle itself, therefore each motor must be able to move up to 250lbs. You
may choose the voltage the motor runs at by selecting the battery voltage, but the minimum motor
voltage must be greater or equal to 12V, while the maximum voltage the motor cannot exceed 96V. You
may choose the voltage, and the motor volume necessary given the constraints of the vehicle. (Note that the orientation of location of the motor is arbitrary however the transmission may not exceed a 50:1
reduction in speed and increase in torque due to efficiency and backlash requirements.) The vehicle
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must be able to vary its velocity from full stop to full speed, while also moving in both a forward and
reverse direction.
Part 1) Motor Design and Analysis. Design a motor that will be able to be used for the four motors in
the Autohauler drive system.
The motor will have a designed efficiency of 60%. That is, the mechanical power realized is 60% of the
electrical power applied. The frequency response of the motor must allow frequencies up to 10 KRad/S
to be applied to it before attenuation of the applied voltage, i.e. the motor cut-off frequency when not
moving is 10 KRad/S
A.
Describe your design of the motor to include the following:
a. The field & armature resistance
b. The value of the inductance.
c. The amount of current draw of the motor for the required torque.
d. Draw a schematic of the electrical model of your motor?
Provide all equations in the analysis and selection of the design criteria with justification.
B.
At the motor’s full rotational velocity, what is the calculated back emf of the motor.
If the motor is in a test stand such that it has a moment of inertia of J=0.04 , and damping b=0.2, the
transfer function is described follow as where K is the back emf and torque constant.
𝐻(𝑠) =
C.
𝑅𝑜𝑡𝑎𝑡𝑖𝑜𝑛𝑎𝑙 𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑜𝑢𝑡(𝑠) 𝜔(𝑠)
𝐾
=
=
𝑉𝑜𝑙𝑡𝑎𝑔𝑒 𝑖𝑛𝑝𝑢𝑡 (𝑠)
𝑉(𝑠) [(𝑠𝐿 + 𝑅)(𝐽𝑠 + 𝑏)] + 𝐾 2
Graph the frequency response of H(s) for the magnitude and phase.
Part 2) Drive electronics.
A) Develop a BJT based transistor switching scheme for direction and velocity control that can be
implemented for the designed motor. The input control signals are driven from an embedded
processor that can supply a control current of 10mA. The processor provides to each motor a
speed as a Pulse Width Modulated signal, and a direction signal. If the direction signal is logical
value 0, which is 0V, then the motor rotates clockwise. Likewise, if the direction signal is logical
value 1, which would be 5V, then the motor rotates counter clockwise. Provide details for the
transistor used and justify your choices. Identify all currents and voltages in the design as
necessary. Be sure to explain the theory of operation as to why your approach works.
B) What is the maximum current draw for the motor at the stall condition?
C) What is the maximum power dissipated by each motor driver circuit?
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Part 3) Design Trade
One of the design trades is to add two additional motors to the design (one per side). Excluding cost
weight and complexity, what impact would adding the two additional motors have to your design of the
motor and its frequency response, as well as the electronics driving them? Justify your answers to the
fullest extent possible for full credit.
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