Preliminary Test Results

1
Preliminary Test Results

• Senior Project 2003/2004
• Matt Greytak
• December 5, 2003

2
Project Overview

• Fall 2003
• Build boat model powered by dual waterjets,
  controlled remotely through an on-board computer
• Waterjet thrust vectoring in two axes yaw and
  pitch
• Run boat in Charles River, collect acceleration
  and pitch/roll data while planing in waves
• Winter
• Analyze data
• Develop dynamic model for system
• Develop control system to minimize slamming and
  pitch/roll accelerations
• Spring 2004
• Integrate control system into on-board computer
• Run boat in Charles River with control system in
  place and without
• Analyze acceleration and pitch/roll data compare
  performance with and without control system

3
Boat Construction

• 11/32 plywood frames
• 1/2 basswood keel
• 5/32 square balsa chine sheer strips
• 1/8 marine plywood sheeting
• Fixed to frames with brass tacks and epoxy
• Epoxy coating, inside and out
• Prevents rot
• Smooth hull surface on bottom

4
Boat Construction
5
Motor Specs andDry Performance

• Nominal voltage 12 V, Max voltage 19.2 V
• Peak efficiency 75 current draw at peak
  efficiency 7 Amps at 12 V
• Current-limited at 45 Amps
• No-load RPM at 12 V
• Port motor 10,000 RPM
• Starboard motor 9,800 RPM
• Each draws 2 Amps

6
Waterjet Specs

• 11 total length
• 40 mm impeller diameter
• Integrated dual rudders on each waterjet to turn
  flow

7
Waterjets
Rudders built into waterjets pitch control not
yet implemented
8
Electronics Summary
Servos / Speed Controllers
Rx
Port Throttle
Tx
Star Throttle
Throttle, rudder, and pitch
Sensors
Port Rudder
Tied electronically
TT8 Logs sensor and command data, and passes Rx
signals to servos
Heave Accel.
Star Rudder
Port Pitch
Pitch Tilt
Not yet implemented
Star Pitch
9
Power Management
Speed Controllers
Port Motor
12V Lead-Acid Power Battery
Port
Stbd
Stbd Motor
Control Signal
Heave Accel.
TT8
9V Batt
9V Batt
Rx
4.8V Batt
Pitch Tilt
10
TT8 Program

• Initialize choose a write line to memory
  interval (1 write every line) and a write
  memory to disk interval (1 write to disk every
  line this slows down the program)
• Loop 25 Hz (no timing or delays)
• Read inputs from receiver on TPU lines
• Write outputs to servos on TPU lines
• Read sensor data
• On write line to memory loop, print data to a
  string
• On write memory to disk loop, print string to
  data file
• Usually choose to write line to memory every
  loop, and write memory to disk every 50 loops
  (2 seconds)

11
Final Hull Specifications

• LOA 44
• LWL 36
• Max Waterline Beam 10
• Draft 1.25
• Dry (no lead-acid battery) weight 4.87 kg
  10.73 lb
• CG 15 from stern

12
Tow Tank Testing 11/25/03
Sits at design waterline
Waterjets at full throttle
13
Tow Tank Testing 11/25/03
Achieves full plane (movie)
14
Tow Tank Testing 11/25/03
High-frequency hull slamming when planing
mV
Starboard list due to off-center 12V lead-acid
battery
Time (sec)
Data results, centered - Roll and pitch 35 mV
per degree - Acceleration 500 mV per g
15
River Testing 11/26/03

• Goals
• Evaluate overall performance in waves (will it
  plane?)
• Collect slamming acceleration data from river
  waves
• Results
• Pair of (temporary) 6V batteries too heavy sat
  low in water
• Could not achieve a full plane in waves
• Significant radio interference limited control

16
River Testing 11/26/03
Power batteries 2 large 6V in series
17
River Testing 11/26/03
Wave height 2-3 inches boat struggles
18
River Testing 11/26/03
Boat achieves half-plane
19
River Test Conclusions

• Need lighter batteries
• New 6V batteries have arrived by mail
• Need more power
• 3 new 6V batteries can be combined in series to
  18V, max allowed by motors total weight less
  than 2 old batteries
• Data collected but Flash disk corrupted by file
  transfer attempt. No data to analyze.

20
Future Winter Testing

• River test Wednesday 12/10/03, 11AM at Sailing
  Pavilion existing system with 18V
• Design and implement pitch control surfaces in
  jet stream
• Measure thrust and torques in Tow Tank to
  evaluate waterjet and control surface performance
• River test with pitch control if weather permits