Tab. 1.
Anthropometric data
| Anthropometric variables | Dimension[mm] |
|---|---|
| Index Finger Tip | 37 |
| Index Finger Middle | 38 |
| Index Finger Bottom | 39.90 |
| Pinky Finger Tip | 27.92 |
| Pinky Finger Middle | 30.40 |
| Pinky Finger Bottom | 31.85 |
| Thumb Tip | 31.50 |
| Thumb Middle | 34 |
| Thumb Lower | 44.5 (Palm End)-24(Thumb lower end) |
| Palm | 97.45 |
| Wrist Forearm Section (2) | 30.85 |
| Upper Forearm | 110 |
| Middle Forearm Section | 112 |
Fig. 1.
Parts of the bionic-hand: a) lower forearm, b) middle forearm, c) wrist, d) palm, e) thumb, and f) finger
Fig. 2.
Exploded view of the model
Fig. 3.
String-operated index finger construction
Tab. 2.
Component list
| Components | Specifications |
|---|---|
| Power Source | 2200mah,11.1v rechargeable Lithium polymer battery |
| Microcontroller | Arduino UNO R3 |
| sEMG Sensor | MYOWARE V2.0 (Sparkfun) |
| Vibration Motor | 3V,10mm coin motor |
| Pressure Sensor | FSR402 |
| Servo Voltage regulator | LM2596 DC-DC |
| Thermal Sensor | MLX90614 |
| Temperature regulator | Heated pad |
| Servo Motors | MG996R(Towerpro) |
Fig. 4.
Circuitry system: a) Circuit diagram for movement control, b) Circuit design of thermal sensor and heating pad control
Fig. 5.
Force diagram: a) tension generated on the string by the servos, b) index finger, c) force diagram of thumb
| Symbols | Descriptions | Value |
|---|---|---|
| τ | Servo stall torque (MG996R) | 1.0 N·m |
| D1 | Shaft radius used for tendon tension | 0.00775 m |
| D2 | Knuckle-to-fingertip distance | 0.065 m |
| D3 | Knuckle Diameter | 0.005 m |
| D4 | Knuckle Diame-ter(thumb) | 0.009 m |
| F2 | Tendon tension | 129 N |
| F1 | Fingertip force (four fingers) | 9.92 N |
| F3 | Fingertip force( thumb) | 18.4N |
| m1 | Mass per finger | 1.01 kg |
| m2 | Thumb mass-equivalent | 1.87 kg |
| Total (curled) | 4×m1,curled + m2 | 10.6 kg |
Fig. 6.
Functional demonstration of lifting ability: a) Hand in no grip position( no lifting force), b) lifting the weight horizontally, c) lifting the weight vertically
Fig. 7.
Program Flow
Fig. 8.
sEMG Signals picked from Flexor carpi ulnaris for pattern 1 and pattern 2
Fig. 9.
Control of the servos: a) Signals picked while flexing the muscle with high intensity, b) sEMG signal to servo angle mapping
Fig. 10.
Different object gripping capabilities:a) Holding an object with a rough surface (pattern 2), b) Holding an object with a smooth surface (pattern 2), c) gripping with three fingers (pattern 2)
Tab. 3.
Feedback from FSR
| Sensor Input | Nature of Responses |
|---|---|
| 500 | Too sensitive (vibrator auto vibrates after each delay time) |
| 700 | Less sensitive (if something moves near the FSR touch pad vibrator vibrates) |
| 900 | For instance, environmental factors, ex, if the wind blows, FSR reads the signal and the vibrator vibrates |
| 1000 | The vibrator stopped vibrating due to movements, but was too responsive to touch. |
| 1022 | The response was good as only forcing the finger on the FSR would make the motor vibrate. |
| 1100 | The FSR touchpad needed to be pressed harder for a response in the vibrator |
Fig. 11.
Sensor location and data: a) thermal sensitivity data, b) location of the sensors
Fig. 12.
Accuracy of the system in responding to desired input signals