Current Design Prototype

Latest Prototypes

Actuators: Ultrasonic Motors

Ultrasonic motors appear as a very interesting technology for a wearable skin stretch device. Some of the advantages that they present are:

• High output torques
• Compact
• Light
• No backdriveable (suited for low power consumption)

We were a little bit worried about vibrations, but after the first test we check that the operation of this kind of actuators is very smooth. In fact the driving frequency is around 50kHz. Maybe the main problem that they present is their durability and robustness.

Some general information about this technology can be found in SurveyOperatingPrinciples_UltrasonicPiezomotors.pdf: Various operating principles of Ultrasonic Piezomotors

The ultrasonic motor that we are testing is a USR30 E3a from http://www.shinsei-motor.com/

It’s main technical specifications are:

• Driving frequency 50kHz
• Rated torque 0.05Nm
• Rated rotational speed 250rpm
• Maximun torque 0.1Nm
• Holding torque 0.1Nm
• Weight (included encoder) 65g

• shinsei_Catalog_E_2005_09.pdf: Shinsei Catalog

Sensors

In order to design a wearable system we need very compact subsystem. Here we have some of very compact rotary sensors that we are considering to add to the final device.

• absolutemagneticencoderMA3_USdigital.pdf: Miniature Absolute Magnetic Shaft Encoder

• miniatureencoderomsT_nemicon.pdf: Miniature optical encoder

• E4miniatureencoderUSdigital.pdf: US digital miniature optical encoder

• opticalencoder_AV01-0286EN.pdf: Module optical encoder

Trasmission

We just assembly a first prototype with an ultrasonic motor, an encoder and a compact cable transmission in order to obtain more output torque and to have a “desktop” system based in this technology.

• The transmission ratio is 5, so the output torque of the system is 0.5Nm.
• The maximum ration angle is around 330deg.

Here are some pictures of the prototype001:

• proto001_01.jpg:
  

• proto001_02.jpg:
  

• proto001_03.jpg:
  

• proto001_04.jpg: