Motors & Motor Controllers ECE 450

AC or DC Motors AC DC Few robots use AC except in factories Most of those that use AC first convert to DC DC Dominates in robotics Must be bidirectional

DC Motor Types Continuous-duty (run continuously when power supplied) Brushed Brushless Servo Intermittent-duty (power must be pulsed to run continuously) Stepper Motors

Motor Specifications Operating voltage Current draw Speed Torque Stalling or Running Torque

DC Motor: Brush Motors The most common. Toys, battery powered tools, electric machines. Stator (permanent magnets) Brushes

Brush DC Motors Identify: Stator Rotor Brushes Commentator Permanent Magnets Armature Field Electrical Engineering Terms: Armature: The power-producing component of an alternator, generator, dynamo or motor. The armature can be on either the rotor or the stator. Field: The magnetic field component of an alternator, generator, dynamo or motor. The field can be on either the rotor or the stator and can be either an electromagnet or a permanent magnet. http://mot-sps.com/motor/tutorial/blac.html

Brush DC Motor How does it work?

Pulse Width Modulation (PWM) Centered PWM

Brushless DC Motor Identify: Permanent Magnets Rotor Brushes Commentator Armature Field http://mot-sps.com/motor/tutorial/blac.html

Brushless DC Motor Laminated steel stack Winding Shaft Permanent Magnets Less common. Higher efficiency, less friction, less electrical noise. Requires electronic driver.

Brushless DC Motor How does it work?

DC Servo Motor A DC Servo Motor is a DC Motor with Gears and Electronics with limited angular rotation (typically 90, 180 or 360º) Why the addition of gears? Nylon Karbonite Metal Why electronics? Digital Analog http://www.societyofrobots.com/actuators_servos.shtml

Requires constant pulsing ( 50 times / second) DC Servo Motor 2.00 ms 1.50 ms 1.00 ms 0.50 ms 0.00 ms 1 1.50 ms: Neutral 1.00 ms: 0 degrees 2.00 ms: 180 degrees Requires constant pulsing ( 50 times / second) http://www.seattlerobotics.org/guide/servos.html

DC Servo Motor Wiring to Microcontroller Servo motors have three wires: power, ground, and signal. The ground wire is typically black or brown and should be connected to a ground . The power wire is typically red, and should be connected to the voltage source. The signal pin is typically yellow, orange or white and should be connected to the microcontroller

Stepper Motors Very common. Required driver. Very strong, when not rotating. Easy to control rotor position. Unipolar* Bipolar The stepper motor rotates in set angles for each pulse received. Typical angles are turns 30º, 15º and 7.5º. * An 8 lead stepper is wound like a unipolar stepper, but the leads are not joined to common internally to the motor. http://www.stepperworld.com/Tutorials/pgUnipolarTutorial.htm

Stepper Motor Controllers With the appropriate logic, step motors can be bi-directional, synchronous, provide rapid acceleration, stopping, and reversal, and will interface easily with other digital mechanisms. They are further characterized as having low rotor moment of inertia, no drift, and a noncumulative positioning error. Generally step motors are operated without feedback in an open-loop fashion and sometimes match the performance of more expensive DC Servo Systems. The only inaccuracy associated with a step motor is a noncumulative positioning error measured in % of step angle. http://www.anaheimautomation.com/intro.htm http://arduino.cc/en/Reference/StepperUnipolarCircuit

Stepper Motor Full Step Half Step Very common. Required driver. Very strong, when not rotating. Easy to control rotor position. Full Step Half Step http://mot-sps.com/motor/tutorial/blac.html

Full-Step Stepper Motor 1 1 1 1

Half-Step Stepper Motor 1 1 1 1 1

Using an Atmel Tiny2313 and SN754410 H-Bridge http://www.instructables.com/id/Drive-a-Stepper-Motor-with-an-AVR-Microprocessor/

Motor Drivers Simple, 1- dc motor (brushes), on/off driver DC Brush D1 1N5817 (Schottky) M C Q1 2222A (NPN) B On: to +9 V Off: to GND or disconnected R1 1 k E

Transistors PNP Bipolar Transistor NPN Bipolar Transistor C B E C B E http://www.kilowattclassroom.com/Archive/AN0007.pdf

DC Brushed Motor Drivers Simple, 1-motor, on/off driver 1 k E Q2 2907A (PNP) On: to GND or disconnected Off: to +9 V B C M1 DC Brush M D1 1N5817 (Schottky)

Motor Drivers Classic Bipolar H-Bridge On: to GND or disconnected Off: to +9 V On: to GND or disconnected Off: to +9 V D1 1N5817 (Schottky) M M1 DC Brush +9 V Q2 2907A (PNP) R2 1 k B C E R1 D2 Q1 2222A (NPN) Q4 R4 R3 Q3 D3 D4 Terminal 4 Terminal 2 Terminal 3 Terminal 1 On: to +9 V Off: to GND or disconnected On: to +9 V Off: to GND or disconnected Taken from Intermediate Robot Building by David Cook

Motor Drivers Classic Bipolar H-Bridge 1 k E R2 1 k D4 1N5817 (Schottky) D2 1N5817 (Schottky) E B B Q4 2907A (PNP) C C from microcontroller 4427 1 2 3 4 8 7 6 5 NC GND IN A IN B VDD OUT A OUT B Q2 2907A (PNP) M GND Q3 2222A (NPN) Q1 2222A (NPN) from microcontroller M1 DC Brush R3 1 k C D1 1N5817 (Schottky) C R1 1 k D3 1N5817 (Schottky) B B E E Taken from Intermediate Robot Building by David Cook

Motor Drivers Typical H-Bridge Motor Driver DC Brush OUT B +5 VDC Disconnected or from microcontroller From microcontroller SN754410 1 2 3 4 ENABLE A&B OUTPUT A INPUT A GND 5 6 7 8 INPUT B OUTPUT B VMOTOR VLOGIC OUTPUT C INPUT C INPUT D OUTPUT D ENABLE C&D 16 15 14 13 12 11 10 9 from microcontroller M2 0.1 F 220 F +4.5 to +36 VDC Taken from Intermediate Robot Building by David Cook