**5. Results and discussion**

During experimentation, the input parameter from muscle ranging from ±1.2 mV is taken through referenced single-ended (RSE) signal along with continuous sampled pulses. These pulses are amplified with the help of a PXI system (amplification factor 2550). The desired output voltage range is generated through a DAC output port. The output signal is connected to IPMC based artificial muscle finger. Due to amplified output voltage from the DAC, an IPMC strip bends in one direction for holding the object. By changing the movement of human finger in an opposite direction, reverse behaviour of IPMC is obtained. The characteristics of IPMC based artificial muscle finger are traced on a graph paper and plotted as shown in Fig. 13. It shows that IPMC based artificial muscle finger gives similar bending behaviour as a human finger (Fig. 14). It is also observed that the deflection of IPMC based artificial muscle finger changes with voltage upto 12 mm in one direction. When this finger moves reverse direction, the characteristic of artificial finger does not attempt the same behaviour. It shows the error between two paths is 0.5 mm. The deflection characteristic of IPMC based artificial muscle finger (δ*)* in term of voltage *(V)* with cubic behaviour for holding is given below,

$$\delta(V) = 0.67 \times \text{V}^3 \text{-} 1.9 \times \text{V}^2 \text{+3.7} \times \text{V} \text{ -0.17 (in mm)} \tag{9}$$

Computational Intelligence in Electromyography Analysis – 376 A Perspective on Current Applications and Future Challenges

the execution of the program when the warning flag has a high output. The flow chart for actuation of IPMC based artificial muscle finger is shown in Fig. 12. During operation, artificial muscle finger bends in a similar manner as that of the index finger. For generating force, this finger is held in cantilever configuration on the fabricated work bench. A load cell is used to collect the data at different angles of the index finger. The current and voltage analysis of the human muscles are also done through oscilloscope. Thus an IPMC artificial muscle finger based micro gripper driven by EMG is developed and the holding behaviour is demonstrated.

Power supply Power supply

**Figure 11.** Basic testing layout for actuation of IPMC based artificial muscle finger

Human finger IPMC finger

During experimentation, the input parameter from muscle ranging from ±1.2 mV is taken through referenced single-ended (RSE) signal along with continuous sampled pulses. These pulses are amplified with the help of a PXI system (amplification factor 2550). The desired output voltage range is generated through a DAC output port. The output signal is connected to IPMC based artificial muscle finger. Due to amplified output voltage from the DAC, an IPMC strip bends in one direction for holding the object. By changing the movement of human finger in an opposite direction, reverse behaviour of IPMC is obtained. The characteristics of IPMC based artificial muscle finger are traced on a graph paper and plotted as shown in Fig. 13. It shows that IPMC based artificial muscle finger gives similar bending behaviour as a human finger (Fig. 14). It is also observed that the deflection of IPMC based artificial muscle finger changes with voltage upto 12 mm in one direction. When this finger moves reverse direction, the characteristic of artificial finger does not attempt the same behaviour. It shows the error between two paths is 0.5 mm. The deflection characteristic of IPMC based artificial

PID Control System

*)* in term of voltage *(V)* with cubic behaviour for holding is given below,

=× × × ( ) 3 2 ( ) 0.67 V -1.9 V +3.7 V -0.17 in mm *V* (9)

IPMC Control

Circuit PXI System

DAQ assistant

**5. Results and discussion** 

ADC/DAC

muscle finger (

δ

δ

**Figure 12.** Flow chart of for actuation IPMC based artificial muscle finger using EMG signal

Computational Intelligence in Electromyography Analysis – 378 A Perspective on Current Applications and Future Challenges

**Figure 13.** Deflection behaviour of IPMC based artificial muscle finger with different voltages

**Figure 14.** Control of IPMC based article muscle finger through EMG signal (Jain et al., 2011)

(a) Initial state (b) Activated state

Design and Control of an EMG Driven IPMC Based Artificial Muscle Finger 379

=× × × ( ) 3 2 *F V*( ) 0.11 V +0.25 V +1.6 V-0.11 in mN (10)

For generating force by the artificial muscle finger, a testing setup with load cell is used. The IPMC based artificial muscle finger is placed in cantilever mode, and a load cell is placed under the tip of the IPMC which produces the reactive force. When human finger moves downward, the generated force by IPMC artificial muscle finger increases accordingly in the

By controlling the movement of human finger, the generated force varies accordingly. The generated force characteristic with voltage shows a cubic polynomial behaviour as shown in Fig. 16 when IPMC artificial muscle finger touches the load cell. This happens due to compliant behaviour of IPMC. The generated force (*F)* by IPMC based artificial muscle

Generated force by IPMC artificial muscle finger with voltage

Curve fitted behaviour

Force generated by IPMC artificial muscle finger

**Figure 16.** Generated force by IPMC based artificial muscle finger at tip with voltage

θ

The maximum generated force of 10 mN is achieved by IPMC based artificial muscle finger at 450 angle of index finger with cubic polynomial behaviour as shown in Fig. 17. This happens due to human finger behaviour where EIP and EDC muscles are connected with DIP and PIP joints. The generated force *(F)* by IPMC based artificial muscle finger at tip in

0 0.5 1 1.5 2 2.5 3

Voltage (V)

For observing the real time IPMC based artificial muscle finger behaviour with moving human finger angle, experiments are conducted and data are plotted as shown in Fig. 18 and it shows almost proportional behaviour with quadratic relationship. This occurs due to human finger behaviour where EIP and EDC are connected with IO and LU muscles (Fig. 3).

 θ×× × ( ) 3 2 F( ) = - 0.000083 + 0.01 - 0.063 + 0.045 in mN (11)

*)* is also obtained as under

θθ

load cell as shown in Fig. 15.

term of human finger angle *(*

θ


0

2

4

Generated force by IPMC artificial muscle finger (mN)

6

8

10

finger in term of voltage (*V*) is given below,

**Figure 15.** Load test setup for IPMC based artificial muscle finger using load cell

For generating force by the artificial muscle finger, a testing setup with load cell is used. The IPMC based artificial muscle finger is placed in cantilever mode, and a load cell is placed under the tip of the IPMC which produces the reactive force. When human finger moves downward, the generated force by IPMC artificial muscle finger increases accordingly in the load cell as shown in Fig. 15.

Computational Intelligence in Electromyography Analysis – 378 A Perspective on Current Applications and Future Challenges

0

2

X: 0 Y: 0.5

4

6

Deflection of IPMC artificial muscle finger (mm)

8

10

12

**Figure 13.** Deflection behaviour of IPMC based artificial muscle finger with different voltages

0 0.5 1 1.5 2 2.5 3

Behaviour of IPMC artificial muscle finger with voltage X: 3

Behaviour of IPMC finger for holding Reverse behaviour of IPMC finger

Y: 12

Voltage (V)

**Figure 14.** Control of IPMC based article muscle finger through EMG signal (Jain et al., 2011)

(a) Initial state (b) Activated state in ACW direction

**Figure 15.** Load test setup for IPMC based artificial muscle finger using load cell

(a) Initial state (b) Activated state

By controlling the movement of human finger, the generated force varies accordingly. The generated force characteristic with voltage shows a cubic polynomial behaviour as shown in Fig. 16 when IPMC artificial muscle finger touches the load cell. This happens due to compliant behaviour of IPMC. The generated force (*F)* by IPMC based artificial muscle finger in term of voltage (*V*) is given below,

=× × × ( ) 3 2 *F V*( ) 0.11 V +0.25 V +1.6 V-0.11 in mN (10)

**Figure 16.** Generated force by IPMC based artificial muscle finger at tip with voltage

The maximum generated force of 10 mN is achieved by IPMC based artificial muscle finger at 450 angle of index finger with cubic polynomial behaviour as shown in Fig. 17. This happens due to human finger behaviour where EIP and EDC muscles are connected with DIP and PIP joints. The generated force *(F)* by IPMC based artificial muscle finger at tip in term of human finger angle *(*θ*)* is also obtained as under

$$\mathbf{F}(\theta) = -0.000083 \times \theta^3 + 0.01 \times \theta^2 - 0.063 \times \theta + 0.045 \quad \text{(in mN)}\tag{11}$$

For observing the real time IPMC based artificial muscle finger behaviour with moving human finger angle, experiments are conducted and data are plotted as shown in Fig. 18 and it shows almost proportional behaviour with quadratic relationship. This occurs due to human finger behaviour where EIP and EDC are connected with IO and LU muscles (Fig. 3). The relationship between IPMC based artificial muscle finger displacement (δ) and human finger angle *(*θ*)* is given below,

$$\mathcal{S}(\theta) = -0.0016 \times \theta^2 + 0.34 \times \theta - 0.15 \text{ (in mm)}\tag{12}$$

Design and Control of an EMG Driven IPMC Based Artificial Muscle Finger 381

Cases Intrinsic muscles Extrinsic muscles State Polarity

**Table 1.** Analysis of different condition of muscles

mentioned conditions from muscles.



IPM C A

ctuation V

 oltage(V

 )


E M G V oltage(V )

0

1

<sup>2</sup> x 10-3

**Figure 19.** Different voltage responses in real time environment

 IO 1 IO 2 LU EDC EIP FDS FDP Side A Side B 1 OFF OFF OFF OFF OFF OFF OFF None None None 2 ON OFF ON OFF OFF ON ON Adduction +ive -ive 3 OFF ON ON ON ON OFF OFF Abduction -ive +ive 4 ON ON ON ON ON ON ON None None None

The two surfaces of IPMC are denoted as side A and side B. In case of intrinsic muscles, the adduction is possible. When IO 1 or IO 2 are in either "on" or "off" condition along with LU muscle in "on" condition then it shows the abduction state. In case of extrinsic muscles, EDC and EIP muscles both are in "off" condition to achieve the adduction state when FDS and FDP muscles both are in "on" condition and for attaining the abduction state EDC and EIP both are in "on" condition when FDS and FDP both are in "off" condition. In rest cases, no power is achieved. Therefore, IPMC based artificial muscle finger is activated in above

The voltage characteristic behavior is taken from EMG and fed to IPMC based artificial muscle finger for actuation in real time environment as shown in Fig. 19. It is found that the

EMG Voltage vs. Time

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Time(s)

IPMC Actuation Voltage vs. Time

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Time(s)

trend of IPMC actuation voltage is similar to EMG voltage with amplification factor.

**Figure 17.** Generated force by IPMC based artificial muscle finger with human finger angle

**Figure 18.** Relationship between IPMC based artificial muscle finger and human finger angle

For actuation of IPMC based artificial muscle finger, the analysis of activated muscles is carried out as given in Table 1. We have analysed different conditions during contraction of different muscles of index finger like intrinsic and extrinsic which are responsible for actuation of IPMC based artificial muscle finger so that they can be used to hold an object.


**Table 1.** Analysis of different condition of muscles

Computational Intelligence in Electromyography Analysis – 380 A Perspective on Current Applications and Future Challenges

*)* is given below,

δ θ


IPMC finger displacement (mm)

0

2

4

Force generated by IPMC artificial muscle finger (mN)

6

8

10

12

finger angle *(*

θ

The relationship between IPMC based artificial muscle finger displacement (

*( ) = - 0.0016 + 0.34* × ×− θ

Curve fitted behaviour

**Figure 17.** Generated force by IPMC based artificial muscle finger with human finger angle

IPMC finger behaviour Curve fitted behaviour

0 5 10 15 20 25 30 35 40 45

Human finger tip angle (deg)

IPMC finger displacement Vs Human finger tip angle

**Figure 18.** Relationship between IPMC based artificial muscle finger and human finger angle

For actuation of IPMC based artificial muscle finger, the analysis of activated muscles is carried out as given in Table 1. We have analysed different conditions during contraction of different muscles of index finger like intrinsic and extrinsic which are responsible for actuation of IPMC based artificial muscle finger so that they can be used to hold an object.

0 5 10 15 20 25 30 35 40 45

Human finger tip angle (deg.)

( ) <sup>2</sup>

 θ

Force generted by IPMC artificial muscle finger with human finger tip angle

Force generated by IPMC artificial muscle finger

δ

0 15 . in mm (12)

) and human

The two surfaces of IPMC are denoted as side A and side B. In case of intrinsic muscles, the adduction is possible. When IO 1 or IO 2 are in either "on" or "off" condition along with LU muscle in "on" condition then it shows the abduction state. In case of extrinsic muscles, EDC and EIP muscles both are in "off" condition to achieve the adduction state when FDS and FDP muscles both are in "on" condition and for attaining the abduction state EDC and EIP both are in "on" condition when FDS and FDP both are in "off" condition. In rest cases, no power is achieved. Therefore, IPMC based artificial muscle finger is activated in above mentioned conditions from muscles.

The voltage characteristic behavior is taken from EMG and fed to IPMC based artificial muscle finger for actuation in real time environment as shown in Fig. 19. It is found that the trend of IPMC actuation voltage is similar to EMG voltage with amplification factor.

**Figure 19.** Different voltage responses in real time environment

The EMG voltage *VEMG (t)* and IPMC actuation voltage *VIPMC actuation (t)* equations are respectively given below,

$$V\_{EMG}(t) = \sum V\_{0E} \sin(2\pi f\_{0E}t + \delta\_{0E}), \qquad 0 \le t \le 0.1\tag{13}$$

Design and Control of an EMG Driven IPMC Based Artificial Muscle Finger 383

so that an IPMC based artificial muscle finger is activated by EMG signal via human finger. The packing tape is also placed on the tip of IPMC based artificial muscle finger so that this finger perfectly holds the object like micro pin for assembly. After these observations, it is understood that IPMC finger behaves as an artificial muscle and this characteristic is implemented in the development of IPMC artificial muscle finger based micro gripper for holding the object through EMG. The major advantages of EMG-driven IPMC based artificial muscle finger are low voltage in man-machine interface, large bending amplitude

In order to develop the micro/bio-mimetic robot for micro assembly, the potential of an EMG driven artificial finger is discussed in this chapter. An artificial finger for micro assembly is designed using IPMC where IPMC is used as an active artificial finger for holding the object. An IPMC has several advantages such as actuating through a small voltage (±3 V), light in weight, flexible in nature and does not involve sophisticated controllers for operation. For activating the IPMC based artificial finger, voltage is taken from human index finger through EMG sensor instead of battery source as this is used as a man-machine interface device. Principally, EMG sensor acquires the signal from body during expansion or contraction of muscles. These movements are transferred into an IPMC based artificial muscle finger. For achieving the stable data from EMG, different configurations of control methods are analysed. A PID control system is implemented for attaining the noiseless and stable signal from the user's myoelectric signal. While acquiring the data, a differential amplification technique is applied where data is filtered through a band pass filter and noise is eliminated through three band stop filters. For sending this signal to the IPMC, an algorithm has been developed in Labview software which gives

• Acquire voltage data (±1.2mV) from human index finger using EMG sensor through

• Amplify the continuous EMG signal through DAQ assistant enabling the filter and

• Activate IPMC finger through amplified data (±3V) using interface device for

Experimentally, it is demonstrated that IPMC based artificial muscle finger is capable of adopting this voltage from EMG signal and mimics as a human finger. From application point of view, an IPMC artificial finger based micro gripper is developed and its capability is also verified. Through this demonstration, it is proved that IPMC can be activated through EMG signal and is applicable as flexible and compliant finger for holding the object in the fields of micro manipulation. IPMC based artificial muscle could also be a replacement of an electro-mechanical system like electric motors in the application field of

and simple control that are applied in development of micro/bio robot.

**6. Conclusion** 

emphasis on following points:

data acquisition system

rehabilitation technology.

domain frequency range options

functioning as artificial muscle finger

and

$$V\_{\text{IPMContration}}(t) = \sum V\_{01} \sin(2\pi f\_{01}t + \delta\_{01}), \qquad 0 \le t \le 0.1 \tag{14}$$

Where, *V*0E is average value of EMG voltage (V); *f*0E is EMG frequency range (Hz) ; *t* is signal sample time (s) ; δ0E is phase difference when signal is taken through EMG (rad); *V*0I is average value of IPMC actuation voltage (V); *f*0I is IPMC actuation frequency range (Hz); δ0I is phase difference when signal is given to IPMC (rad). For finding the frequency range of each signal, the experimental data are taken and solved through MATLAB curve fitting tool. The numerical values are *V*0E= 0.001451±0.0002707 V, *f*0E= 4.7±0.006201 Hz, δ0E= -1.736±0.036 rad, *V*0I= 2.493±0.208, *f*0I= 48.5±0.65 and δ0I= -10.5732±0.6556 rad. From these data, it is found that EMG frequency range (*f01)* is similar to simulated data and IPMC actuation frequency range is 48.5±0.65 Hz which is in between human muscle frequency range (48-52Hz).

**Figure 20.** IPMC based artificial muscle finger based micro gripper driven by EMG

After these analyses, an IPMC artificial muscle finger based micro gripper is developed which is driven by EMG as shown in Fig. 20 where one IPMC based artificial muscle finger and other plastic based finger are fixed with double sided tape within one holder. The IPMC based artificial muscle finger is connected through copper tape and wire with EMG sensor so that an IPMC based artificial muscle finger is activated by EMG signal via human finger. The packing tape is also placed on the tip of IPMC based artificial muscle finger so that this finger perfectly holds the object like micro pin for assembly. After these observations, it is understood that IPMC finger behaves as an artificial muscle and this characteristic is implemented in the development of IPMC artificial muscle finger based micro gripper for holding the object through EMG. The major advantages of EMG-driven IPMC based artificial muscle finger are low voltage in man-machine interface, large bending amplitude and simple control that are applied in development of micro/bio robot.
