1) The current through a diode is given by Id = Idss(ekV/T

-1), Id is the current through the diode; V is the

diode voltage; T is the temperature in Kelvin, Idss is the “reverse saturation current” which you can assume is constant; and k is a constant. For a particular application, it is proposed to measure the temperature from measurements of Id and V.

i) Solve the equation for the temperature in terms of other variables. ii) Given Idss = 10

-9 A and at T=298 K, V=0.6 V, Id=0.1 A, find k.

iii) Using the value of k calculated above, if V=0.65V and Id=0.1A, what is the temperature?

iv) If V=0.01V and Id=0.001A, assuming independent measurement errors, what is the uncertainty in the temperature calculation? NB: d/dx(logex) = 1/x

2) A power line inspection robot was discussed in the class. It has four cameras for navigation and

another camera for line inspection. Each joint motor and each gripper motor has its own microprocessor, current and position sensing and motor drive. In addition, there is a high speed processor on the inspection camera to process inspection images and another high speed processor for overall control and for communication with the ground station. Discuss the principles of Brookes’ subsumption architecture for this robot. (10)

3) SuperRay Torpedo

Figure 4: Torpedo being fired by gunship

The Navy has contracted your company to develop a new homing torpedo for use on gunships. As part of the design team, the details you have been given are as follows:

V

Id

The concept of operation

The torpedo is required to be a semi-active guided system. This means that the torpedo should only start emitting its SONAR signal, once the system is within a certain distance threshold. This will ensure that firing the torpedo will not give away the position of the ship.

So, when fired the torpedo is given a latitude, longitude and depth. It will then steer and ensure that it is on track towards this point and also that is at a depth of at least 500m below sea level. This will be called “Position Mode”. Once it is close enough (<1 km), it must engage “Homing Mode”, where its SONAR will illuminate the target, and allow fine tracking. Once it is as close as (<10m) it must detonate (Detonation Mode).

If during Position mode any of the subsystems malfunction, the torpedo must go into “Abort Mode” and just float to the surface and disengage all armaments. If during Homing mode, the SONAR signal loses the target the (no signal), the torpedo must also enter Abort Mode.

Target

Homing Mode

Position Mode

Last Known Position

Gun Ship

Figure 1: Concept of operation for the SuperRay Torpedo. The first stage (Position Mode), the torpedo motions towards the last known position of the target. Once the torpedo is within 1km of target it switches to Homing Mode where it actively seeks and steers towards the target signal. Once it is close enough, the torpedo will enter Detonation mode.

From the datasheet, the SONAR receiver sensor outputs a voltage that is linearly proportional to distance to the target. The relationship is graphically depicted below:

a) If you are using the ADC of the STM32, what would the distance be if the ADC data register contained the value of 0xDAC. Assume 12 bit mode. [3 marks]

b) The homing guidance algorithm is shown below:

gain

Antenna Position 66.67

PWM

The target position is provided by an ADC voltage taken from the seeker antenna from 0 to 3.3V. Where 1.5V means the antenna is in the centre position and thus, when the seeker antenna is at 1.5V, the PWM duty cycle output should be zero.

Using this information, write a C function that converts the ADC value of the seeker and outputs the appropriate PWM duty cycle.

Use the function prototype ‘float32_t homingControl(uint16_t ADCVal)’

[4 marks]

4) Digital filter A simple example of a low pass filter is the Infinite Impulse Response (IIR) filter. This is realized by the following equation:

𝑦𝑛 = 𝑥𝑛𝛼 + (1 − 𝛼)𝑦𝑛−1 Where, 𝑦𝑛 is the filter output at the current sample, 𝑦𝑛−1 is the filter output of the previous sample, 𝑥𝑛

is the filter input and 𝛼 is the product of the filter cut-off (in rad/s) and the sample time in (s). a) Write a low pass filter function. Assume the following function prototype: [5 marks]