208 lines
6.5 KiB
Markdown
208 lines
6.5 KiB
Markdown
# Automotive Gearbox Control System - Specification
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## 1. System Overview
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The Automotive Gearbox Control System is an electronic control unit (ECU) that manages gear shifting in a semi-automatic transmission. The system monitors vehicle conditions and driver inputs to determine optimal gear selection and execute smooth gear changes.
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## 2. System Components
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### 2.1 Input Sensors
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- **Vehicle Speed Sensor**: Measures current speed (0-200 km/h)
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- **Engine RPM Sensor**: Measures engine revolutions (0-7000 RPM)
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- **Throttle Position Sensor**: Measures accelerator pedal position (0-100%)
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- **Brake Pressure Sensor**: Detects brake application
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- **Clutch Position Sensor**: Monitors clutch engagement state
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- **Gear Position Sensor**: Detects current gear (N, 1-6, R)
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### 2.2 Driver Controls
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- **Gear Selector**: Manual, Sport, Eco modes
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- **Shift Paddles**: Manual up/down shift requests
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- **Clutch Pedal**: Manual clutch control (if applicable)
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### 2.3 Outputs
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- **Gear Actuator**: Mechanical gear selection
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- **Clutch Actuator**: Clutch engagement/disengagement
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- **Dashboard Display**: Current gear indicator
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- **Warning Lights**: System errors and alerts
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## 3. Operating Modes
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### 3.1 Manual Mode
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- Driver has full control over gear selection
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- System prevents invalid shifts (e.g., direct 5th to 1st)
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- Rev-matching on downshifts
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- Neutral safety: requires brake to shift out of Park/Neutral
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### 3.2 Sport Mode
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- Holds gears longer for higher RPM
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- Faster gear changes
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- Downshifts on hard braking
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- Target shift points: 5000-6500 RPM
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### 3.3 Eco Mode
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- Early upshifts for fuel efficiency
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- Target shift points: 2000-3000 RPM
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- Smooth, gradual gear changes
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- Skip-shift capability (e.g., 2nd to 4th)
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## 4. Functional Requirements
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### 4.1 Gear Shifting Logic
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#### 4.1.1 Upshift Conditions
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- **Eco Mode**: Engine RPM > 2500 AND throttle < 40%
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- **Manual Mode**: Driver paddle input OR RPM > 6000
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- **Sport Mode**: Engine RPM > 5500
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#### 4.1.2 Downshift Conditions
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- **Eco Mode**: Engine RPM < 1500 OR heavy throttle (>80%)
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- **Manual Mode**: Driver paddle input OR RPM < 1200
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- **Sport Mode**: Engine RPM < 2000 OR brake pressure > 50%
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#### 4.1.3 Prohibited Shifts
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- Cannot shift from Reverse to any forward gear without stopping (speed = 0)
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- Cannot shift to Reverse from any forward gear while moving (speed > 0)
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- Cannot skip more than 2 gears in a single shift (except computer-controlled skip-shift)
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- Cannot downshift if resulting RPM would exceed 7000 (red line protection)
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### 4.2 Safety Features
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#### 4.2.1 Hill Start Assist
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- Activates when: stopped on incline > 5% AND brake released
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- Holds brake pressure for 2 seconds
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- Prevents rollback
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#### 4.2.2 Overrun Protection
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- Prevents downshift if resulting engine RPM > 6500
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- Displays warning message to driver
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- Ignores paddle input if unsafe
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#### 4.2.3 Stall Prevention
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- Auto-downshift if engine RPM < 800 while moving
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- Automatic neutral engagement if stopped for > 3 seconds in gear
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- Clutch slip if speed drops below minimum for current gear
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#### 4.2.4 Neutral Safety
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- Engine start only allowed in Park or Neutral
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- Brake pedal required to shift from Park
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- Reverse requires full stop (speed = 0 km/h)
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### 4.3 Error Handling
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#### 4.3.1 Sensor Failures
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- **Speed Sensor Failure**: Limit to current gear, disable automatic shifting
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- **RPM Sensor Failure**: Use speed-based shift logic as fallback
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- **Throttle Sensor Failure**: Default to conservative shift points
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- **Multiple Sensor Failures**: Enter limp-home mode (3rd gear only)
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#### 4.3.2 Actuator Failures
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- **Gear Actuator Jam**: Attempt 3 retries with 200ms delay
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- **Clutch Actuator Failure**: Lock in current gear, display warning
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- **Hydraulic Pressure Low**: Reduce shift speed, display warning
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#### 4.3.3 Temperature Management
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- **Normal Operation**: 70-110°C
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- **High Temperature Warning**: 110-130°C (reduce shift frequency)
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- **Critical Temperature**: >130°C (limp-home mode, 3rd gear only)
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## 5. Performance Requirements
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### 5.1 Shift Times
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- **Eco Mode**: 800-1200 ms per shift
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- **Manual Mode**: 400-600 ms per shift
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- **Sport Mode**: 150-300 ms per shift
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### 5.2 Response Times
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- **Paddle Input**: < 50 ms recognition
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- **Brake Detection**: < 20 ms
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- **Emergency Neutral**: < 100 ms
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### 5.3 Reliability
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- **MTBF**: > 150,000 km
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- **Shift Success Rate**: > 99.5%
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- **False Error Rate**: < 0.1%
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## 6. Environmental Conditions
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### 6.1 Operating Temperature
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- **Normal**: -20°C to +50°C ambient
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- **Gearbox Oil**: -10°C to +130°C
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### 6.2 Altitude
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- **Sea Level to 3000m**: Normal operation
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- **3000m to 5000m**: Adjusted shift points for reduced air density
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### 6.3 Weather Conditions
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- Rain, snow, ice: Reduced shift aggressiveness
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- Detection via wheel slip sensors and ABS integration
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## 7. User Interface Requirements
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### 7.1 Dashboard Display
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- Current gear number (1-6, R, N, P)
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- Selected mode (Manual, Sport, Eco)
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- Shift indicator (up/down arrows)
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- Warning messages (text + icon)
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### 7.2 Warning Messages
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- "Gearbox Overheating" (yellow)
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- "Shift Not Possible" (red)
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- "Service Required" (yellow)
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- "Limp-Home Mode Active" (red)
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### 7.3 User Feedback
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- Shift confirmation (subtle indicator flash)
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- Paddle input acknowledgment (haptic feedback if available)
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- Audio warning for critical errors
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## 8. Integration Requirements
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### 8.1 Engine Control Unit (ECU)
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- Torque reduction request during shifts
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- RPM synchronization for smooth engagement
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- Engine braking coordination
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### 8.2 Anti-lock Braking System (ABS)
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- Wheel slip detection for traction control
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- Emergency braking gear hold
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- Stability control integration
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### 8.3 Electronic Stability Control (ESC)
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- Torque vectoring support
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- Drift mode compatibility (sport mode)
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- Traction control coordination
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## 9. Validation Requirements
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### 9.1 Unit Testing
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- Individual sensor input validation
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- Shift logic decision trees
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- Safety feature triggering
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### 9.2 Integration Testing
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- Multi-mode operation
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- Sensor failure scenarios
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- ECU communication
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### 9.3 System Testing
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- Real-world driving scenarios
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- Extreme condition testing
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- Long-term reliability testing
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## 10. Constraints and Assumptions
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### 10.1 Physical Constraints
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- Maximum gear ratio: 1:6.5 (1st gear) to 1:0.85 (6th gear)
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- Clutch engagement time: 200-400 ms
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- Hydraulic system pressure: 8-12 bar
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### 10.2 System Assumptions
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- Sensors provide accurate readings within ±5% tolerance
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- ECU communication latency < 10 ms
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- Battery voltage maintained at 12-14V
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### 10.3 Regulatory Compliance
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- ISO 26262 (Automotive Safety Integrity Level - ASIL C)
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- UNECE R13 (Braking regulations)
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- Local emissions standards compliance
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