Automated Snow Shovel

1. Automated Snow Shovel Team 33 Fiona Chen, Dian Hua Lin, Dominic Poon Spring 2008 ECE 445 Senior Design

2. Overview • Introduction • Features • Sensors • Ultrasonic Sensor • Tachometer • Actuator • FPGA Board • Connecting to FPGA • Analog-to-Digital Converter (ADC) • Current Amplifier Bridge (CAB) Module • Voltage Step Down • Conclusion

3. Introduction • Background • Commercial snow shovels are human driven • Primitive snow shovels • Problems • Manpower wastage • Inconvenience • User-unfriendly GOAL: To design a automated snow shovel to solve the existing problems

4. Features • Detection of concrete-snow boundary via ultrasound technology • Programmable search pattern via FPGA board • Error detection via tachometer sensing • Resistance to extreme temperature

5. Features: Search Pattern Start Search Pattern Shovel snow for distance x Make U-turn Repeat steps 3 and 4 until reach other side of pavement Go to new section of pavement and repeat from step 3

6. Sensor/Device Layout Top view: Wheel not connected to motor V. US tachometer Actuator S H O V E L - + Left Wheel Power Supply H. US ECE 110 motorized vehicle H – Horizontal V – Vertical US – Ultrasound Sensor Right Wheel Power Supply - + Actuator V. US

7. Sensor/Device Layout Power Supply - + Side View: Actuator H. US V. US tachometer Actuators Front View: H. US V. US V. US SHOVEL tachometer Rotating axle Unmotorized wheel

8. Ultrasonic sensors 400ST/R120 • works on the principle of different attenuation • constants (α ) of materials •  | V(receiver) | = | V(transmitter) | exp (-α z) • soil has higher α than concrete •  absorbs more wave energy •  reflects less wave energy •  receiver voltage output would show smaller • magnitude when reflecting off soil than off • concrete • can also be used to distinguish distance between • sensors and reflecting material • z  | V(receiver) | for same α 400ST 400SR air Incident wave Reflected wave Snow/soil/ concrete Absorbed wave

9. Ultrasonic sensors Determining optimum transmitter input • Ideal inputs: • 40kHz • 10Vrms • Our transmitter input: • 40kHz square wave 10VP-P • FPGA 3.3Vp-p generated wave had to undergo CMOS amplification before input into transmitter 400ST/R 120 Data sheet

10. Ultrasonic Sensors • Vertical Sensors: • To distinguish between soil and concrete to determine necessity of snow shovelling • Receiver outputs for vertical sensors 2” above material: • Horizontal sensors: • To determine if there is an obstruction in front of vehicle • Receiver outputs for horizontal sensor at 5” in front of obstruction:

11. Ultrasonic Sensors • voltage outputs insufficiently high for • voltage comparison in a comparator • had to amplify receiver output via • op-amp LM6181 • Op-amp outputs: • Voof each amplified ultrasonic sensor output fed into different voltage comparators +5V Vo 400SR + - 1kΩ -5V 4.7kΩ Voltage Compatator Vo Output To FPGA Board 2.6V

12. Tachometer • Consists of an LED and a BJT • If BJT receives light from LED, BJT has non-zero base and collector currents •  Vo is low • If BJT does not receive light from LED, BJT has zero base/collector currents •  Vo is high

13. Tachometer • Application in our design: • wheel is expected to move if vehicle motor is on (entire vehicle moves) • wheel does not move while motor is on • (i.e. all 3 other wheels are moving) •  vehicle is stuck • Vehicle calls for help if it gets stuck • Normal Operation •  axle continuously rotates •  tachometer alternately blocked and unblocked •  Vo,max≠ Vo,min • Vehicle is stuck •  axle stops rotating •  tachometer stays either blocked or unblocked •  Vo,max = Vo,min Vo to FPGA board De-motorized wheel tachometer Axle attached to wheel

14. Tachometer Circuit: tachometer output & Logic: OPB 818 + S 1kΩ +5V 1 2 + E 4 3 • Vo fed into comparator at Vdiff = 2.5V • Output from comparator sent to FPGA board • FPGA analyzes whether Compmax = Compmin • If Yes, FPGA outputs a signal to wirelessly call for help Vo 100Ω +5V

15. Linear Actuator + V - + - • Operation: • Metal piece is attracted to actuator if V = 10V •  shovel is raised • Metal piece is released from actuator if V = 0V •  shovel is lowered • Logic: • Shovel is lowered only when shovelling takes place • Shovel is up in search pattern • Shovel is down when shovelling • Shovel is up when calling for help Linear Actuator A420- 065973- 00 Metal piece connected to shovel axle

16. FPGA Board • FPGA board is used to control the car’s movements • DE2 board chosen as it has 2 40-pin expansion ports with about 36 available pins each 40-pin IDE expanson ports

17. FPGA Board: Outputs • FPGA board outputs 3.3V for high, 0V for low • Board logic uses 5V and 0V • Motors / Actuators run on 10V

18. FPGA Board: Outputs • Wheel Motor outputs • Forward and backwards • Variable speed • Shovel control • 40kHz square wave • Distress signal

19. FPGA Board • Digital output pins used to drive motor of car with variable speed for turns • Multiple sensors to determine surrounding and car will be able to react accordingly

20. FPGA Board: Inputs • Ground ultrasound sensor • Sampling rate: 1kHz • Forward ultrasound sensor • Sampling rate: 1kHz • Ground speed sensor • Sampling rate: 0.2 Hz

21. FPGA Board: Features • Motor is not powered after 5s of car being immobile • Car is stopped immediately if the forward sensor detects something • Proximity of about 5 to 10 cm away from shovel

22. Connecting to FPGA: Block Diagram FPGA Board Ultrasound Sensor ADC/ DAC Tachometer ADC Voltage Step-up Actuator Wheel Motors CAB

23. Analog-to-Digital Converter:Voltage Comparator Circuit • FPGA logic • High: 3.3V • Low: 0V • Sensor output above 2V corresponds to a FPGA high Reference Voltage (2V) 3.3V Resistor Sensor Input LM3302 FPGA Input

24. Current Amplifier Bridge (CAB) • To input FPGA signals to control movement of the car motor MJE3055T MJE3055T MJE3055T MJE3055T

25. 5V 7.5V 10V CA3600 40 kHz 3.3Vp-p Ground Digital to Analog Converter:CMOS Amplifier 40 kHz 10Vp-p

26. FPGA Input to Actuator 10V From Voltage Comparator MJE3055T Actuator + Actuator -

27. THANK YOU