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 (They spec parts not sure which drivers they use)
  • [X] Figure out max current draw. (10A starting current)
  • [ ] Develope Model of Motor and get Frequency Response
  • [ ] Find and purchase Flat Flex Cable (FFC) connectors
  • [ ] Purchase large mosfets for testing
  • [ ] Purchase Surfboard for mounting DSC
  • [ ] Build test rig
• [ ] Finalize on a DSC
• [ ] Choose MOSFETS
• [ ] Sample all the parts
• [ ] Schematic Design
• [ ] Build prototype
• [ ] Prototype evaluation
• [ ] 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

• Depletion Mode
• Probably an NMOS and a PMOS
• The FETS have to be able to handle 10A drain current
• Matrix of Potential FETS

Schematics

Schematics

Parts

Now under consideration; commutation on the FPGA.

DSC

On Semiconductor MC33033

Quick Specs

• 10 to 30 V Operation
• Undervoltage Lockout
• 6.25 V Reference Capable of Supplying Sensor Power
• Fully Accessible Error Amplifier for Closed Loop Servo Applications
• High Current Drivers Can Control External 3-Phase MOSFET Bridge
• Cycle-By-Cycle Current Limiting
• Internal Thermal Shutdown
• Selectable 60° /300° or 120° /240° Sensor Phasings
• Also Efficiently Control Brush DC Motors with External MOSFET H-Bridge

Data Sheet

MC33033 Datasheet (PDF)

Articles

Modeling a DC motor Brush-Less Motor Simulink

Links

• Electrical System