ECE6,4990-02 Actuators and sensors

From Ece

This page contains a list of actuators and sensors discussed in ECE6,4990-02 Intro to Robotics.

Actuators

• Sprawl is an example of a family of robots using both pneumatic and hydraulic actuators.
• The OCTOR robot is driven by pneumatic actuators.

H-bridges

More H-bridges are available from ST, TI, Toshiba, and Allegro, National, and Intersil (formerly Harris). Linear Technologies probably also sells them, but I haven't searched for them. There's a short Wikipedia article on H-bridges.

Motors

• The control of stepper motors tutorial is excellent. See also another tutorial and the stepper motor information and technical forum.
• Info on servos can be found in experiment 11 of ECE3724 lab manual. There's also an article on how servos work and a guide to servos.
• Maxon makes fantastic motors. Many motors are designed to fit with encoders that snap on the back of the motors; see e.g. the technology pdf.
• (Unconfirmed) Faulhaber and its two partners, Minimotor and MicroMotor sell very small motor, gearbox, and encoder combinations.

The Robocoaster shows the ability of electric motors to drive high loads.

Sensors

Distance

3D

• The SICK 3-D laser rangefinders are excellent. For example, the Sick LMS 200 does 180 degree scans in 0.25 degree increments up to 80m with 10mm resolution, resulting in 3D data of the area.

2D

• A cheaper alternative (~$2700) is a Hokuyo URG-04LX 2-D laser rangefinder, ± 10 mm at 0.36 degree resolution. They have other sensors as well.
• An IR rangefinder, the Hokuyo PBS series, is even less expensive.

1D

• The Sharp GP2D series IR distance sensors are around $10.
  • The required cable and connector can be purchased from a robotics store: Acroname R47-JSTCON-2. Acroname has a nice guide to the various flavors.
  • Or, the connector and pins for the connector can be purchased from Digi-Key. The required connector is a JST PN PHR-3. The matching contacts are JST SPH-002T-P0.5S. This information is available in Sharp's FAQs. It's also listed in the PDF version of the Digi-key catalog just after the sensors themselves; see for example the catalog page of Digi-Key 425-1810-ND.
  • Page 4 of the application note gives instructions for mounting the sensor depending on the direction of movement of the sensed object.
• The Devantech ultrasonic rangefinders come in several varieties. The cheapest starts at $29. Other vendors such as Parallax and C-Stamp also sell them.

Vision

• The CMUCam tracks objects of a given color; about $170 for the CMUCam2+.

Encoders

Several companies produce them; one is US Digital, which aims at the more professional (re: accurate and expensive) market. Vendors:

• CTS makes mechanical encoders, which have a shaft (rather than locking onto a shaft). They're about $3 from DigiKey; see also DigiKey's part search -> switches, encoders -> encoders.
• Grayhill also makes cheap ($5 from Digikey) mechanical and optical encoders such as the 62P series. Like CTS, they're for human interface and consequently have a shaft which the human spins.
• The US Digital E4P is about $20 (in large quantities) and fits a wide variety of shafts. It requires some assembly, for you which you need a spacer tool and possible a centering tool (if you use the adhesive mount); see the "accessories" link on the E4P page.
• Nubotics makes an encoder which mounts to Solarbotics motors and wheels. However, they're unreliable.
• The Vex robotics optical shaft encoders work, but they aren't quadrature: they sense motion, but not the direction of motion (forward or backward). The same is true of Parallax's encoders.
• Active robots sells a somewhat expensive quadrature encoder.
• You can build your own by printing an encoder pattern using software from the website then add that to an IR emitter/detector.

Line sensors

There's a lot of these available. One option that's worked well at MSU is the Fairchild QRD1114.

Vendors

• Acroname
• Sparkfun
• Lynxmotion
• Servo city for servos
• Solarbotics for motors and wheels
• Pololu for motors, wheels, casters