Millions of people in the U.S. suffer from impaired hand function due to a stroke which impacts the use of either one or multiple fingers.

Standard devices to solve this issue, such as exoskeletons, while being incredibly precise they are known to introduce many issues, some of which include:• Cost – These devices range in the thousands of dollars

and are not available to everybody who needs one.• Weight – These devices are made of heavy metal

components that will affect the motion of users• Comfort – Fitting rigid metal components will

produce compression forces against soft tissue

PROBLEM

SOLUTION

Sensor Manufacturing

METHODOLOGY IMPLICATIONS

The final purpose of this research involves using the data collected from the sensor glove and applying it to a supernumerary device similar to that shown below.

Supernumerary robotic (SR) devices are a class of wearable device which adds extra limbs to the user to enhance manipulation capabilities. In order to add this device to a person, we need to be able to map the different forces and gestures that a person uses for various grasping motions.

Embedding these sensors to the soft robotic phalanges would allow us to introduce the same haptic feedback loop that was implemented with the glove and a healthy hand.

Future steps involves fitting one of these devices in an individual with an impaired hand and seeing how well the device can compliment the patients limited range of motions.

REFERENCES(1)Arduino.com, (2)Sparkfun.com

ACKNOWLEDGEMENTI would like to thank Dr. Hammond for giving me the opportunity to work in such exciting research as well as for his excellent guidance through out this process.

To solve this problem a supernumerary robotic (SR) device is proposed to add additional grasping capabilities. This device is attached to the body and would act by coordinating with the patient and complimenting their motions through feedback from the human to the robot as well as from the robot to the human.This device will be a soft robotic one made of mostly silicone, which would solve the problems stated above:• Cost – Silicone sensor and devices can be made much

more readily and are molded easily thus reducing cost of manufacturing.

• Weight – The silicone being used in these components has a density that’s a fraction of that of its metallic counterpart.

• Comfort – Silicone easily conforms to the body of the wearer and safely provides the motive forces required to actuate human joints.

The George W. Woodruff School of Mechanical EngineeringFernando de Caralt

Soft Sensors for Coordination of Robot-Assisted Grasping

Sen

sor

Resp

onse

(V)

Applied Load (N)

0.5

0.42

0.46

0.38

0.3

0 0.2 0.4 0.6 0.8 1.0

0.34

Tensile Load at 29% Strain

(0.637 N)

Tensile Strain Response

Off-Axis Compression

Predicted Response

Sen

sor

Resp

onse

(V)

0.8

0.1

0.4

0.6

0.5

0.7

Applied Pressure (kPa)

0.3

0.2

0.0

0 20 40 60 80 100 120

Loading

Unloading

Voltage at Sensor Bias Resistance (1.86 Ohms)

Actual Response

Predicted Response

RESULTS

Pressure SensorStrain Sensor

Resistance Change vs. Strain Relationship

∆𝑅𝑒𝑥𝑡=𝜌 𝐿h𝑤 { 1

1−2 (1−𝜈2 )𝑤 𝜒 𝑝 /𝐸 h−1}

Resistance Change vs. Pressure Relationship

Vibratory motor

Hand acts on sensor

Sensor relays output to

microcontroller

Microcontroller processes input

Output sent to haptic feedback

Receive input from haptic feedback and adapt grasp

Haptic Feedback Loop

The finalized glove is composed of a pressure sensor located on the tip of the index finger in addition to a strain sensor that is placed above the knuckle of the same finger. The sensors were compared to theoretical models in order to be calibrate them. The sensor data follows the models accurately, especially for the strain sensor. This data can then be used to predict the sensors response for a range of forces in order to set a feedback loop between the sensor and the proposed SR device.A haptic feedback system was implemented in order to relay the information from the sensors back to the user, this was done by detecting the change in the resistance of the sensors through a voltage divider, amplifying this voltage by using a non-inverting amplifier and then setting ranges of voltages in which the vibratory motor will send a signal back to the user.

(1)

(2)

Impaired fingers