RC08Brushless

In 2008 RoboCup switched to brushless DC motors. While brushless motors are smaller and far more efficient than brushed motors the commutation normally performed inside a brushed DC motor will need to be done externally using some control circuitry. There are two main parts to our brushless motor controller solution; the controller which uses sensors on the motor to gate signals to one of three coils, and the half-bridge motor drivers which actually drive the coils.For the controller a special-purpose brushless motor driver IC was used. For information on the motors or motor control software please see their respective pages.

Tasks

• [ ] Get the motor and begin playing with it
  • [X] Call Maxon and get a recommendation on motor drivers (Note: Already have design for motor drivers)
  • [X] Figure out max current draw. (10A starting current)
  • [X] Develop Model of Motor and get Frequency Response (Note: This is a task to be covered in firmware)
  • [X] Find and purchase Flat Flex Cable (FFC) connectors (Note: Found one)
  • [X] Purchase large mosfets for testing (Note: Test rig built and verified with drive motors)
  • [X] Purchase Surfboard for mounting DSC
  • [X] Build test rig
• [X] Finalize on a DSC (Note: No DSC this year. Doing it in logic)
• [X] Choose MOSFETS
• [X] Sample all the parts
• [X] Schematic Design
• [ ] Build prototype
• [ ] Prototype evaluation
  • [ ] Verify current draw under load especially start-up
  • [ ] Check if there is any temp rise in FETs in continuous operation
• [ ] Make necessary changes

Specifications

Motor Controller Chip

• The motor is spec'd at 12V and is 30W
• A decent transient response (dead-time + switching time)
• 3-Channels in one package
• Braking is not a requirement but would be nice
• High Impedance OFF state
• Fault protection (overvoltage, overcurrent, fast response)
• Small package
• Ability to operate in the >20kHz range
• Gate drive capability (either can directly driver the gate or is open drain.)
• Data sheet recommends a MOSFET
• Matrix of Potential Drivers

MOSFET

• NMOS and a PMOS
• The FETS have to be able to handle 10A drain current
• Matrix of Potential FETS Other FETs we considered

Schematics

• 

  Brushless Motor Driver Schematic

Parts

We are performing commutation on the FPGA with gate drivers.

Gate Driver

Microchip TC4428

• 1.5 A
• 6 mA quiescent
• Noninverting low side
• Inverting high side

FETS

Part No.	Make	Package	ContIDS	MaxIDS	Rds	MaxVGS	Samples	Data Sheet
NTMS4503N N-Channel	ON Semi	SO-8	14 A	--	--	28 V	Y	[1]
NTMS10P02 P-Channel	ON Semi	SO-8	10 A	--	--	20 V	Y	[2]

Motor Connector

Hirose FH12-11S-1SH 11 position 1 mm pitch

Commutation

CW (looking along the shaft toward the motor)

HS 1	HS 2	HS 3	Winding 1	Winding 2	Winding 3
1	0	1	Vcc	Gnd	n.c.
1	0	0	Vcc	n.c.	Gnd
1	1	0	n.c	Vcc	Gnd
0	1	0	Gnd	Vcc	n.c.
0	1	1	Gnd	n.c.	Vcc
0	0	1	n.c.	Gnd	Vcc

CCW (looking along the shaft toward the motor)

HS 1	HS 2	HS 3	Winding 1	Winding 2	Winding 3
1	0	1	Gnd	Vcc	n.c.
1	0	0	Gnd	n.c.	Vcc
1	1	0	n.c	Gnd	Vcc
0	1	0	Vcc	Gnd	n.c.
0	1	1	Vcc	n.c.	Gnd
0	0	1	n.c.	Vcc	Gnd

To find this data:

• Go to https://support.maxonmotor.com/
• Guest Login
• Search for commutation sequence
• First link is "Block Commutation Sequence of maxon EC motors"

I duplicated the tables here because the text on the site is generated by Javascript, the frame URL contains a session ID, and the back button doesn't work.

Articles

Modeling a DC motor Brush-Less Motor Simulink

Links

• Electrical System
• Motor Datasheet: Media:07_197_e.pdf