2. 1. Intake of air + fuel2. Compression3. Combustion 4. Re-compression6. Exhaust 5. Water Injection

3.  Control system must regulate back pressure  Must be inherently stable  +/- 5°C Range  Operate at ~ 1 Hz  Simple = low cost

4.  Regulates back pressure with pressurized air  Inherently unstable  Slower response time  More expensive and possibly dangerous pressures

5.  Regulates back pressure with pump  Inherently stable  Faster response time  Simpler and safer

6.  One input at 75ºC  Variable disturbance due to engine heating  Output temperature in negative feedback  Unknown engine and pump transfer functions

7.  Single transfer function › Relate engine temperature to pump power › Ignores temperature “momentum” › Lagging could cause excessive overshoot (limited allowable overshoot)  Logical case selection › Cases instead of transfer funtion › Temperature difference and momentum define the case › Each case determines a pump power

8. 100°C 90 80 70 60 50

9.  Do not have modified engine  Do not have pump  Manipulate “Engine Temperature” with cold and hot water  Use computer to monitor Controller outputs

10.  AD595 Monolithic Thermocouple Amplifier  Built in cold-junction compensation  10 mV/°C

11.  Arduino Duemilanove prototyping board  ATmega328 processor  Programmed in C

12.  Arduino input is 10 bit resolution along 0 – 5V  Scaling thermocouple amp output to 10 bit resolution › Unit Conversion

13.  High fluctuations in thermocouple › Average over time { temp1 = analogRead(temppin)/2.048; delay(delaytime); temp2 = analogRead(temppin)/2.048; //degrees C delay(delaytime); … oldaveragetemp = newaveragetemp; newaveragetemp = (temp1+temp2+…+temp10)/10; momentum = newaveragetemp - oldaveragetemp; tempdiff=newaveragetemp-desiredtemp; }  Video

17.  Camshaft vs ECU › ECU removes design requirement:  “Control system must regulate back pressure” › Now, control system can regulate injection timing with constant pump pressure › Simpler & cheaper pump › More precise water quantity  Greater averaging of temperatures or filtering to reduce fluctuations › Less toggling of cases › More precise results