MTech Project :
“Development and Analysis of a Soft Humanoid Robot Made up of Flexible fluidic Actuators and Compliant Links”
By Bhushan Darekar MTech Mechatronics College of Engineering Pune
Under the guidance of
Dr. S. S. Ohol
The robot consists of soft compliant links and flexible fluidic actuators that make up the soft arm of the robot designed for payload 500 gram. An arm consists of three Pneumatic Network Actuator(PNA) gripper, a metacarpal joint(palm), a variable stiffness forearm, an elbow joint actuator, a twist actuator and finally a shoulder movement mimicking mechanism. The PNA grippers act as fingers, the elbow actuator acts as the bending joint while the twist actuator induces the twisting action in the arm, all actuators are pneumatically controlled by
Spanda is an intrinsically safe soft humanoid robot made up of flexible actuators and compliant links, capable of working in close proximity with humans.
Spanda (A Soft Humanoid Robot) is the first generation of soft-humanoid robots capable to be used in human assisting functions such as handling objects of different sizes and shapes, as an Assistive Companion, a Navigator, a Walk-through Guide, a child-friendly cuddly robot, etc.
Spanda is inspired
Intrinsic safety is
The field name Soft Robotics itself suggesting the materials used in it has to be soft. Soft Material selection is a vital step in the building of flexible actuators and compliant links.
PDMS(Polydimethylsiloxane) Flex Foam
The soft materials are different types of elastomers and foams and they have a shore A hardness measure. Elastomers and Polyurethane foams are widely used in consumer recreation, Marine and Transportation.
In the Ashby Chart showing these materials have low strength and low density in comparison with metals. For our project work, we needed prototyping material which is Room Temperature vulcanised, so we found out PDMS and Foam materials which are RTV and they are having different shore hardness measure.
Selected three different types of transparent PDMS material ZA13, HT33, HT 45 for this material 13,33 and 45
- B) PDMS Samples (HT 33, HT 45, ZA 13):
PDMS Test Sample a)Before Test b)After Test
- B) Flexible PU foam Samples:
Testing of Hand gripping on variety of shape object
Gripping of different shape objects at pressure 2 bar
Different shape objects can be grasped by the compliant gripper with a three fingers orientation of the hand. All objects are handled at the constant pressure of 2.5 bar.
The objective of design and development of a soft humanoid robot is to perform safe operations in a proximity with humans and this is achieved by partially making robot arm and its Actuators from soft materials. Design and analysis
- PDMS(Polydimethylsiloxane) Elastomers of shore hardness 33A and 45A and Flexible PU foam of shore 00 to 20 Soft materials as per soft humanoid arm requirement has been selected.
- Flexible fluidic actuators with end connectors were built by using PDMS materials having average tensile strength 2.05 MPa and 1.50 MPa.
- 3D printed
moldsare made from PLA (Polylactic Acid) material. These moldswere used to produce the components such as a finger, forearm, elbow actuator etc.
- Pneumatic Network Actuator (PNA)
werebuilt by casting of PDMS material. In testingwe found 3 bar pressures isthe burst pressure for PNA and at 2.5 bar pressure PNA is producing average 5 N force which is sufficient to grip the object of 500 gm
- Elbow actuator
werebuilt by using 3D printed moldsand PDMS casting process. Maximum angle achieved in unloaded condition by elbow actuator is 72 degree .By using test setup, It is found that actuation time for elbow actuator is 4.64 seconds at 2.5 bar and it is producing forceof 20 Newton.
- Twist Actuator of Left and Right helix were built separately by using 3D printed
moldsand PDMS casting process. Maximum Twist produced by twist actuator is 52 degree in unloaded condition at pressure 3 bar with average actuation time of 1.7 seconds. The torque produced by twist actuator is varying between rangeof 2.62 Kgcm at 1bar pressure to 6.88 Kgcm at 3bar pressure. Robotis designed for payloadof 500 gm and in testingit is handling maximumweight of 338 gm. Armhas angularvelocity of 0.3946 rad/sec at 2.5 bar pressure while producing the twist up to 45 degrees and also arm has maximumvelocity of 155 mm/sec while elbowis actuated at pressureof 2.5 bar.
Hence this soft humanoid robot arm having operating parameters as per below
a)Lifting capacity – 338 gm
b)Shoulder movement –
c)Elbow movement –
d)Each finger movement –
e)Total reach of