Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K16/00—Machines with more than one rotor or stator
  • H02K16/04—Machines with one rotor and two stators
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K29/00—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices
  • H02K29/06—Motors or generators having non-mechanical commutating devices, e.g. discharge tubes or semiconductor devices with position sensing devices

Definitions

• This invention relates generally to brushless DC motor systems.
• the invention relates to a brushless DC motor system especially adapted for use in high reliability uses where redundancy is essential, such as in thrust vector control of rocket engines.
• Thrust vector control of rocket engines has in the past been primarily accomplished with the use of hydraulic actuators.
• Hydraulic actuators employing hydraulic pumps while commonly in use, have a disadvantage in that they require high- maintenance costs and suffer from low reliability. More particularly, hydraulic pumps typically run at full speed thereby requiring operation of the hydraulic system controlling the rocket engine to operate at continuous maximum power. Other disadvantages include the fact that they require use of dangerous materials such as hydrazine and are generally very messy due to the presence of hydraulic fluid over the parts.
• Alternative approaches to hydraulic actuators have involved the use of electromagnetic actuators. In comparison to hydraulic systems, electromagnetic actuator systems use much less energy, with a typical hydraulic actuator system using over 34 times as much energy during a mission as a comparable electromagnetic actuator system.
• DC brushless motors are available in several configurations from open loop controlled multi-toothed propelled drives called stepping motors to inside permanent magnet rotor and outside permanent magnet rotor closed loop machines. Due to their wide range of performance and motion control capabilities, such motors are theoretically particularly desirable for use in applications such as rocket vector control, for example, in controlling the direction of orientation of rocket motor nozzles. However, such motors have not been used widely in the field of rocket nozzle control because in the event of shorting of the winding of the motor, the system could experience a catastrophic failure due to the inability to move the DC brushless motor, which locks up upon the shorting of a winding. As may be appreciated, such a failure in the motor can result in a complete and catastrophic failure of the rocket mission.
• the permanent magnet motor system includes a shaft for having multiple permanent magnets mounted thereon, and with the shaft rotatably mounted for rotation about a central axis thereof.
• the permanent magnets are mounted along a predetermined length of the shaft, substantially around the circumference thereof, for causing the shaft to rotate as a result of an inductive force being applied to the permanent magnets.
• At least three windings, each electrically isolated from each other, are arranged around the permanent magnets, each for being individually electrically excited to generate an induction field. The field generated causes the shaft to rotate as a result of the interaction between the generated field and the permanent magnets.
• Individual winding controllers for example, pulse width modulation controller chips, individually control each of the windings in a manner such that should there be a short in one of the windings, the other two windings continue to generate the necessary fields to (1) continue to drive the shaft in a rotational motion, and (2) overcome the drag created by the shorted winding.
• the motor system is fault tolerant taking into account, in a DC brushless motor arrangement, the possible shorting of a winding thereof.
• the windings are preferably arranged in a Y-winding configuration with each of the winding legs parallel to the others. Such a configuration is conventional and well known to those of ordinary skill in the art.
• the winding controllers are insulated gate bipolar transistor power modules.
• the windings comprise at least three windings and more preferably, at least eight. As may be appreciated, in the case with eight windings, should one winding short, the motor will still retain 3/4 of its power due to the loss of one winding by shorting, and another winding being dedicated to overcoming the drag of the winding that shorted. In the case of a single winding shorting in a three winding arrangement, 1/3 power is retained.
• a sensor or sensors are arranged for detecting the rotational position of the shaft.
• the sensor or sensors provide a signal to a motor controller, which controls the insulated gate bipolar transistor power modules of the windings, to issue a control signal to the power modules to excite the windings to cause the shaft to be rotated into a desired position.
• Figure 1 is a schematic diagram of the control circuit architecture and winding arrangement for a DC brushless motor system in accordance with the invention.
• Figure 2 is a second schematic diagram showing the control modules of Figure 1 connected to a motor controller, and with the motor shaft having a position sensor thereon.
• the fault tolerant winding control system in accordance with the invention, is designated generally by the reference number 1 1.
• a single common shaft 13 is shown illustrated in association with redundant windings 17 arranged in a Y configuration about the shaft.
• the shaft 13 includes permanent magnets
• the windings 17 are connected in a manner to be individually and separately electrically excited to generate a field which interacts with the magnets to cause the shaft 13 to rotate.
• Each winding 17 has three legs, 19a, 19b, and 19c, which are arranged in a conventional and well known Y configuration.
• each winding 17 is shown individually controlled by a respective control module 21.
• These modules 21 are, for example, insulated gate bipolar transistor power modules.
• the other redundant windings 17, which are each individually and separately controlled by the power modules 21 through insulated gate bipolar transistors 23a, 23b and 23c, continue to drive the shaft 13 of the motor.
• modules 21 they are conventional and well known to those of ordinary skill in the art. Examples of such commercially available modules include the PWR-82331 high current three-phase bridge power hybrid. Details of such a module are disclosed in the publication by ILC Data Device Corporation PWR-282331 Smart Power Three-Phase Bridge. 1989, which disclosure is incorporated by reference herein.
• a motor controller 27 is employed to control the power modules 21 such that they are synchronized to ensure that the magnets are acted upon by the fields generated by individual windings 17 in a synchronized manner.
• a motor controller 27 is employed.
• Such a controller 27 is conventional and well known and can take the form of, for example, a programmable logic array (PLA).
• PPA programmable logic array
• position sensors 29 can be mounted on the shaft 13 to detect the position of the shaft 13 relative to where it has been commanded by motor controller 27 to be located.
• the position detection sensors 29 provide a position signal to motor controller 27 wherein it is compared to a reference to result in an error signal.
• the error signal is then processed by the controller 27 to generate a signal to the control modules 21 to cause the shaft 19 to be rotated to the desired position correcting for the error until the error signal generated is equal to null.

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• 1993
  • 1993-12-09 EP EP94903543A patent/EP0673559A1/de not_active Withdrawn
  • 1993-12-09 WO PCT/US1993/011956 patent/WO1994014226A1/en not_active Application Discontinuation
  • 1993-12-09 RU RU95114435/07A patent/RU95114435A/ru unknown
  • 1993-12-09 JP JP6514388A patent/JPH08504559A/ja active Pending

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