# WIA-MED-006 PHASE 2: Haptic Feedback Specification

## Overview
This specification defines haptic feedback requirements for surgical robotic systems.

## 1. Force Sensing

### 1.1 Sensor Requirements
- **Force Range**: 0-10N continuous, 0-20N peak
- **Resolution**: 0.1N
- **Accuracy**: ±0.1N or 2% of reading
- **Sampling Rate**: ≥1000 Hz
- **Sensor Types**: Strain gauge, piezoelectric, or 6-axis force/torque

### 1.2 Mounting Locations
- Tool shaft (bending/torsion)
- Tool jaw (grip force)
- Tool base (6-axis F/T)

## 2. Haptic Rendering

### 2.1 Processing Pipeline
1. **Sensor Data Acquisition** (1000 Hz)
2. **Signal Processing**: Noise filtering (Kalman), drift correction
3. **Force Mapping**: Scaling, saturation (max 5N), deadzone (<0.1N)
4. **Tissue Modeling**: K=1-50 N/mm, damping B=0.1-5 Ns/mm
5. **Actuator Drive**: Motor current commands

### 2.2 Performance
- **Update Rate**: 1000 Hz minimum (stability requirement)
- **Total Latency**: <1ms (transparency requirement)
- **Stability**: Guaranteed for passive environments

## 3. Haptic Actuators

### 3.1 Actuator Specifications
- **Force Range**: 0-5N continuous
- **Bandwidth**: DC to 100 Hz minimum
- **Resolution**: 0.05N
- **Backdrivability**: Low friction/inertia

### 3.2 Actuator Types (any compliant)
- DC motors with gearing
- Voice coil actuators
- Piezoelectric actuators
- Pneumatic actuators

## 4. Tissue Models

### 4.1 Standard Tissue Parameters
```
Fat:      K = 1-10 kPa,   High viscoelasticity
Muscle:   K = 10-100 kPa, Medium viscoelasticity
Liver:    K = 5-20 kPa,   High viscoelasticity
Kidney:   K = 10-30 kPa,  Medium viscoelasticity
Vessel:   K = 100-1000 kPa, Low viscoelasticity
Tumor:    K = 50-500 kPa, Low viscoelasticity
Bone:     K = 10-20 GPa,  Very low viscoelasticity
```

### 4.2 Modeling Approaches
- Linear elastic: F = K × x
- Viscoelastic (Kelvin-Voigt): F = K × x + B × v
- Nonlinear: F = K₁×x + K₂×x² + K₃×x³
- Hunt-Crossley (contact): F = K × x^n × (1 + λ × v)

## 5. Validation

### 5.1 Benchtop Testing
- Force accuracy verification
- Frequency response measurement
- Stability testing

### 5.2 Tissue Phantom Testing
- Silicone phantoms with calibrated stiffness
- Porcine tissue comparison
- User studies (N≥10 surgeons)

## 6. Optional Advanced Features

- Texture rendering (vibrotactile 10-300 Hz)
- Thermal feedback
- Multi-point tactile arrays
- Adaptive rendering based on user preference

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**Status**: ✅ Complete  
**Version**: 1.0.0  
**Date**: 2025-01-01

© 2025 WIA · MIT License