This is a simple EMG Controller for a bionic hand prosthesis

Dependencies:   mbed-dsp mbed NOKIA_5110

Galileo Bionic Hand - ST Nucleo Example


This is an example of a simple hybrid sEMG(surface Electromyography) activated controller for the Galileo Bionic Hand Prosthesis implemented with the Galileo EMG Shield. The user has to select the desired posture by sending a special character through serial port (115200 baud rate) and then perform it through sEMG activation by detecting contraction on flexor muscles of the forearm. Contractions on forearm extensor muscles releases the posture and allows the return to the default or rest posture.

Special characters:

  • '1', for "Power Grip" selection
  • '2', for "Point" selection
  • '3', for "Pinch Grip" selection
  • '4', for "Lateral Grip" selection
  • '5' for "Tripod Grip" selection


Galileo EMG Shield - 3 Channels for surface EMG

The electrodes for sEMG are placed on the skin surface and are connected to the input of a precision instrumentation differential amplifier based on Texas Instruments (TI) INA122, then its output is passed through an active low pass filter (LPF) based on TI OPA335 in order to sense the action bio-potentials of the muscular fibers with an output signal span in the range of 0 to 3.3V and a bandwidth between 0 to 500 Hz. The circuit is built-in on a custom PCB with 3 sEMG channels and a bias voltage reference output (1.25 V); furthermore, it is pin compatible with Arduino pin compatible ARM Cortex M4 boards and mbed platform ecosystem (ST Nucleo F411RE, Freescale FRDM K64F, NXP LPCXpresso 4337, ST Discovery F746NG, Renesas GR-Peach, etc), which is ideal for the single ended input of a microcontroller in addition to contributing to low cost development kits. /media/uploads/julioefajardo/shieldbrd.png /media/uploads/julioefajardo/image1.jpg

Electrodes Placement and Connection

Standard surface mounted Ag/AgCl electrodes with wet conductive gels are placed on palmaris longus and extensor digitorum muscles (third channel could be placed on Flexor carpi Ulnaris), focusing only on below elbow disarticulation. These electrodes have been well-characterized and most of its properties are well understood, except for some properties as drifting and low-frequency noise. Nevertheless, with proper preparation of the skin, the sEMG signal is excellent.

Disposable electrodes and snap leads information:

Proper placement of disposable electrodes for two channels of surface EMG is shown below:

/media/uploads/julioefajardo/electrodes.png /media/uploads/julioefajardo/mucles.png

Customizable Postures

You can customize the actions by modifying PWM values (microseconds) on FingerPosition function (values depends on the way that the hand was built it). The prosthesis has five fingers and a thumb rotation mechanism and five actuators in order to perform multiple types of grasping. Wrist rotation will be implement later.

The servo motors have to be connected as shown below:


Function Declaration and Usage Examples

include the mbed library with this snippet

void FingerPosition(float32_t thumb_us, float32_t index_us, float32_t middle_us, float32_t pinky_us, float32_t thumbrot_us);

FingerPosition(2400, 600, 600,2400,2400);   //Close
FingerPosition(2400,2400, 600,2400,2400);   //Point
FingerPosition(2400, 600,2400, 600,2400);   //Pinch
FingerPosition(2400, 600, 600,2400, 600);   //Lateral
FingerPosition(2400, 600, 600, 600,2400);   //Tripod
FingerPosition(1000,2400,2400, 600, 600);   //Open

Serial Oscilloscope Feature

This feature easily allows to watch and log to file the data using serial oscilloscope software (115200 baud rate).

  • Serial_Osciloscope(TRUE,RAW) to watch raw signals, FALSE deactivate this feature
  • Serial_Osciloscope(TRUE,RECTIFIED) to watch rectified signals, FALSE deactivate this feature
  • Serial_Osciloscope(TRUE,SMOOTH) to watch smooth signals, FALSE deactivate this feature


Universal Real-Time Software Oscilloscope GUI information:

Nolia 5110 LCD

Nokia 5110 display implementation for visual feedback will be add later, we have to modify libraries and fonts in order to improve the functionality. The main idea is to change of action by pressing a push button and change thresholds using a potentiometer.



Videos, bill of materials and tutorials to build the Galileo EMG Shield and the Galileo Bionic Hand will be posted soon, more information on:

Wed Sep 30 22:50:24 2015 +0000
Version 1.2

Who changed what in which revision?

UserRevisionLine numberNew contents of line
julioefajardo 0:f2b89c6a8a16 1 #include "mbed.h"
julioefajardo 0:f2b89c6a8a16 2 #include "arm_math.h"
julioefajardo 0:f2b89c6a8a16 3
julioefajardo 4:d8fd3c4484cc 4 #define FLEXION 0.2f
julioefajardo 4:d8fd3c4484cc 5 #define EXTENSION 0.2f
julioefajardo 4:d8fd3c4484cc 6 #define FLEXION2 0.00f
julioefajardo 4:d8fd3c4484cc 7
julioefajardo 0:f2b89c6a8a16 8 Ticker EMG_Sampler;
julioefajardo 0:f2b89c6a8a16 9 Serial pc(SERIAL_TX, SERIAL_RX);
julioefajardo 0:f2b89c6a8a16 10 DigitalOut myled(LED1);
julioefajardo 0:f2b89c6a8a16 11 AnalogIn Ref(A0);
julioefajardo 0:f2b89c6a8a16 12 AnalogIn E1(A1);
julioefajardo 0:f2b89c6a8a16 13 AnalogIn E2(A2);
julioefajardo 0:f2b89c6a8a16 14 AnalogIn E3(A3);
julioefajardo 3:f784301a5166 15 PwmOut Thumb(D11);
julioefajardo 3:f784301a5166 16 PwmOut Index(D10);
julioefajardo 3:f784301a5166 17 PwmOut Middle(D9);
julioefajardo 3:f784301a5166 18 PwmOut Pinky(D6);
julioefajardo 3:f784301a5166 19 PwmOut ThumbRot(D5);
julioefajardo 0:f2b89c6a8a16 20
julioefajardo 0:f2b89c6a8a16 21 float32_t EMG1, EMG2, EMG3;
julioefajardo 2:12f979d695db 22 float32_t samples[25];
julioefajardo 2:12f979d695db 23 float32_t samples2[25];
julioefajardo 2:12f979d695db 24 float32_t samples3[25];
julioefajardo 2:12f979d695db 25 float32_t abs_output[25];
julioefajardo 2:12f979d695db 26 float32_t abs_output2[25];
julioefajardo 2:12f979d695db 27 float32_t abs_output3[25];
julioefajardo 0:f2b89c6a8a16 28 float32_t mean = 0.0f, mean2 = 0.0f, mean3 = 0.0f;
julioefajardo 4:d8fd3c4484cc 29 uint8_t state = 0;
julioefajardo 0:f2b89c6a8a16 30 uint8_t COCO = 0;
julioefajardo 0:f2b89c6a8a16 31
julioefajardo 4:d8fd3c4484cc 32 void ADC_Sampler(void);
julioefajardo 4:d8fd3c4484cc 33 void Close(void);
julioefajardo 4:d8fd3c4484cc 34 void Open(void);
julioefajardo 4:d8fd3c4484cc 35
julioefajardo 0:f2b89c6a8a16 36
julioefajardo 0:f2b89c6a8a16 37 int main() {
julioefajardo 0:f2b89c6a8a16 38 pc.baud(115200); //Serial com at 115200 bauds
julioefajardo 4:d8fd3c4484cc 39 EMG_Sampler.attach(&ADC_Sampler, 0.001); //1 ms ticker for ADC Sampler
julioefajardo 3:f784301a5166 40 //Open -> 0.6ms - Close 2.4ms
julioefajardo 3:f784301a5166 41 Thumb.period(0.02f/2.0f);
julioefajardo 3:f784301a5166 42 Thumb.pulsewidth(0.0010f/2.0f);
julioefajardo 3:f784301a5166 43 //Open -> 2.4ms - Close 0.6ms
julioefajardo 3:f784301a5166 44 Index.period(0.02f*2.0f);
julioefajardo 3:f784301a5166 45 Index.pulsewidth(0.0024f*2.0f);
julioefajardo 3:f784301a5166 46 //Open -> 2.4ms - Close 0.6ms
julioefajardo 3:f784301a5166 47 Middle.period(0.02f*2.0f);
julioefajardo 3:f784301a5166 48 Middle.pulsewidth(0.0024f*2.0f);
julioefajardo 3:f784301a5166 49 //Open -> 0.6ms - Close 2.4ms
julioefajardo 3:f784301a5166 50 Pinky.period(0.02f*2.0f);
julioefajardo 3:f784301a5166 51 Pinky.pulsewidth(0.0006f*2.0f);
julioefajardo 3:f784301a5166 52 //Open -> 0.6ms - Close 2.4ms
julioefajardo 3:f784301a5166 53 //ThumbRot.period(0.02f/2.0f);
julioefajardo 3:f784301a5166 54 ThumbRot.pulsewidth(0.0006f*2.0f);
julioefajardo 3:f784301a5166 55
julioefajardo 0:f2b89c6a8a16 56 myled = 1;
julioefajardo 0:f2b89c6a8a16 57 while(1) {
julioefajardo 0:f2b89c6a8a16 58 if(COCO){
julioefajardo 2:12f979d695db 59 arm_abs_f32(samples, abs_output, 25); //rectifier
julioefajardo 2:12f979d695db 60 arm_abs_f32(samples2, abs_output2, 25); //rectifier
julioefajardo 2:12f979d695db 61 arm_abs_f32(samples3, abs_output3, 25); //rectifier
julioefajardo 4:d8fd3c4484cc 62 arm_mean_f32(abs_output, 25, &mean); //mean
julioefajardo 4:d8fd3c4484cc 63 arm_mean_f32(abs_output2, 25, &mean2); //mean
julioefajardo 4:d8fd3c4484cc 64 arm_mean_f32(abs_output3, 25, &mean3); //mean
julioefajardo 4:d8fd3c4484cc 65 //pc.printf("%.10f,%.10f\n\r",mean,mean2);
julioefajardo 4:d8fd3c4484cc 66 switch(state){
julioefajardo 4:d8fd3c4484cc 67 case 0: {
julioefajardo 4:d8fd3c4484cc 68 if (mean>FLEXION){
julioefajardo 4:d8fd3c4484cc 69 myled = 0;
julioefajardo 4:d8fd3c4484cc 70 state = 1;
julioefajardo 4:d8fd3c4484cc 71 Close();
julioefajardo 4:d8fd3c4484cc 72 }
julioefajardo 4:d8fd3c4484cc 73 } break;
julioefajardo 4:d8fd3c4484cc 74 case 1: {
julioefajardo 4:d8fd3c4484cc 75 if (mean2>EXTENSION){
julioefajardo 4:d8fd3c4484cc 76 myled = 1;
julioefajardo 4:d8fd3c4484cc 77 state = 0;
julioefajardo 4:d8fd3c4484cc 78 Open();
julioefajardo 4:d8fd3c4484cc 79 }
julioefajardo 4:d8fd3c4484cc 80 }
julioefajardo 0:f2b89c6a8a16 81 }
julioefajardo 0:f2b89c6a8a16 82 COCO = 0;
julioefajardo 0:f2b89c6a8a16 83 }
julioefajardo 0:f2b89c6a8a16 84 }
julioefajardo 0:f2b89c6a8a16 85 }
julioefajardo 4:d8fd3c4484cc 86
julioefajardo 4:d8fd3c4484cc 87 void ADC_Sampler() {
julioefajardo 4:d8fd3c4484cc 88 EMG1 = (*3.3f;
julioefajardo 4:d8fd3c4484cc 89 EMG2 = (*3.3f;
julioefajardo 4:d8fd3c4484cc 90 EMG3 = (*3.3f;
julioefajardo 4:d8fd3c4484cc 91 //pc.printf("%.10f,%.10f,%.10f\n\r",EMG1,EMG2,EMG3);
julioefajardo 4:d8fd3c4484cc 92 //pc.printf("%.10f,%.10f\n\r",EMG1,EMG2);
julioefajardo 4:d8fd3c4484cc 93 uint32_t m = __get_PRIMASK();
julioefajardo 4:d8fd3c4484cc 94 __disable_irq();
julioefajardo 4:d8fd3c4484cc 95 for(int j=24;j>0;j--) {
julioefajardo 4:d8fd3c4484cc 96 samples[j]=samples[j-1]; //Fill Array
julioefajardo 4:d8fd3c4484cc 97 samples2[j]=samples2[j-1]; //Fill Array
julioefajardo 4:d8fd3c4484cc 98 samples3[j]=samples3[j-1]; //Fill Array
julioefajardo 4:d8fd3c4484cc 99 }
julioefajardo 4:d8fd3c4484cc 100 samples[0]=EMG1;
julioefajardo 4:d8fd3c4484cc 101 samples2[0]=EMG2;
julioefajardo 4:d8fd3c4484cc 102 samples3[0]=EMG3;
julioefajardo 4:d8fd3c4484cc 103 __set_PRIMASK(m);
julioefajardo 4:d8fd3c4484cc 104 COCO = 1;
julioefajardo 4:d8fd3c4484cc 105 }
julioefajardo 4:d8fd3c4484cc 106
julioefajardo 4:d8fd3c4484cc 107 void Close(void){
julioefajardo 4:d8fd3c4484cc 108 Thumb.pulsewidth(0.0024f/2.0f);
julioefajardo 4:d8fd3c4484cc 109 Index.pulsewidth(0.0006f*2.0f);
julioefajardo 4:d8fd3c4484cc 110 Middle.pulsewidth(0.0006f*2.0f);
julioefajardo 4:d8fd3c4484cc 111 Pinky.pulsewidth(0.0024f*2.0f);
julioefajardo 4:d8fd3c4484cc 112 ThumbRot.pulsewidth(0.0024f*2.0f);
julioefajardo 4:d8fd3c4484cc 113 }
julioefajardo 4:d8fd3c4484cc 114
julioefajardo 4:d8fd3c4484cc 115 void Open(void){
julioefajardo 4:d8fd3c4484cc 116 Thumb.pulsewidth(0.0010f/2.0f);
julioefajardo 4:d8fd3c4484cc 117 Index.pulsewidth(0.0024f*2.0f);
julioefajardo 4:d8fd3c4484cc 118 Middle.pulsewidth(0.0024f*2.0f);
julioefajardo 4:d8fd3c4484cc 119 Pinky.pulsewidth(0.0006f*2.0f);
julioefajardo 4:d8fd3c4484cc 120 ThumbRot.pulsewidth(0.0006f*2.0f);
julioefajardo 4:d8fd3c4484cc 121 }