Why artificial muscles without going to the robots

Why artificial muscles without going to the robots?

Artificial muscle, the name is not very good, but proper names should be called electro-active materials. Because I’m in the direction of underwater, so for example I have an underwater robot for example. Prior to this, needs to talk about related concepts.

For the battery-powered robot driving mechanism (actuator), can be divided into two kinds: one is pure mechanical drive, is a smart material-driven.

Purely mechanical drive naturally rely on Digital Servo and stepper motor, which directly depend on mechanical structure of cooperation and work to drive the robot to operate parts of the body movement of the drive system.

Among them, Digital Servo and stepper motor is a motor, also commonly known as the motor. Their main function is to produce driving torque, as a source of electrical or mechanical power. Digital servos only needs to send a PWM signal can be maintained at a location under, but turning a limited range, usually 180 or 360 degrees and you can’t achieve position control of stepping motor, but can follow a direction has been turned. So, the motor used in robot joint activities, makes it easier for robot movement required.

Why artificial muscles without going to the robots?

Drivers rely on similar to SMA smart materials (shape memory alloy), EMA (electromagnetic actuation), IPMC (ionic polymer metal composite) these Intelligent material power or deformation driver of temperature changes and exercise.

SMA Chinese name of shape memory alloy is heated to fully eliminate the deformation occurs at lower temperatures, recover its original shape before the deformation of alloys. It can be used for alarm control unit and pen drives, etc.

EMA electromagnetic driving, the principle is very simple, the conductor moving relative to the magnetic field, induced in the conductor, conductor induced current and the magnetic field interactions in motion, this is the electromagnetic drives. Because of the electromagnetic force is relatively small, so EMA applied do not need too vigorously can drive. IPMC Chinese name Ionic polymer metal composite material, because of their low drive voltage that can have a greater displacement, so more used in robotics, I use examples to explain this material.

Although on the surface, smart materials and driving is driving a new continent in the field of, seems to be through the dig and large-scale use and greatly reduce the volume of robot, revamp its cold overall. However, smart materials relative to the amount of deformation mechanical drives is limited, accuracy was not enough, so I regret to inform you, the so-called “artificial muscles” in the scope of application of robots is really small.

I am going to IPMC (ionic polymer metal composite) as an example for illustration purpose. Vans waffle

Vans waffle

IPMC characteristics of this material is, you just have it powered up, it will deform.

Is generally applied voltage on the IPMC thickness direction, IPMC anode bending principle see below. That people can take advantage of this feature: deformation – power – driven robot with his body, it has the corresponding movements. And this material is small, light weight and capable of producing large movements, and requires no bearings and sliding parts, low drive voltage. These features look, of course, is better than a motor that big, you can reduce the footprint.

Why artificial muscles without going to the robots?

But the muscle of another character at odds with a significant demand on the robot control was not so good action on the control.

As long as a digital servo for a duty cycle, you can make it around to where we need to. But the deformation of the IPMC is a non-linear process requires little calibration can I last put to use. And he also limited the amount of deformation, most only from direct State bent at 90 degrees, there is a radian, is not ideal.

Therefore, such materials can be used in control where precision is not too high.

For example I want to control a robot, so it mimics the Jet Propulsion model of a contraction of jellyfish, also don’t have control to open, how much shrinkage, as long as they can, and for a robot to swim on the line, such smart materials can occupy a position in the field. 2012 United States Virginia Tech of Intelligent material systems and structures Center Joseph Najem, who by the IPMC actuator to Victorian tubes glowing jellyfish to prototype, design a robotic jellyfish, physical prototype shown in the following figure.

(A) the jellyfish physical prototype of the machine (b) experimental device

Machine jellyfish has a heat-shrinkable polymer film, flexible Chamber, a central column, a platform used for wiring and support drive, 8 are used for maintaining the stability of the upper mast and radiate the IPMC actuator. Jellyfish 20G, 15 cm in diameter, the machine height 5.8 cm. Due to the IPMC materials under electric field will bend, you can build a drive to simulate the jellyfish, the contraction and expansion of the cavity, but unfortunately this robotic jellyfish’s only 0.77mm/s, pace a little disappointment.

All in all, most of the robot control, control accuracy is an important indicator, and given the relatively small range of motion, so called artificial muscles and can’t get a large area of use. iPhone 6 Vans

Editor’s Note: 2 pictures above sources–

1, IPMC materials: Bhandari b, Lee g y, Ahn s h. A review on IPMC material as actuators and sensors: Fabrications, characteristics and applications[J]. International Journal of Precision Engineering & Manufacturing, 2012, 13(1):141-163.

2, the machine the jellyfish physical prototype test equipment: Najem j, Leo d j. A bio-Inspired bell kinematics design of a jellyfish robot using ionic polymer metal composites actuators[C]. SPIE Smart Structures and Materials + Nondestructive Evaluation and Health MonitoringInternational Society for Optics and Photonics, 2012.

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