Patent Application
20100282955
Rotary motors are commonly used to move an object or alter an object. Many motors are used in conjunction with a measurement system that provides positional feedback for closed-loop control of the motor. However, dust and debris in the environment can adversely influence the operation of the measurement system, and ultimately adversely influence the operation of the motor.
The present invention is directed to a measurement system for measuring a rotational position and/or rotational rate of a device. The measurement system can include (i) a measuring assembly having a first measurement subassembly and a second measurement subassembly, and (ii) a coupling assembly having a component coupler and a device coupler. The second measurement subassembly rotates relative to the first measurement subassembly, and the measuring assembly can measure the amount of relative movement between the measurement subassemblies to determine the position of the device. The component coupler is fixedly coupled to the second measurement subassembly so that rotation of the component coupler results in rotation of the second measurement subassembly. The device coupler is fixedly coupled to the device. Further, the device coupler interacts with the component coupler in a non-contact fashion so that the rotation of the device coupler results in rotation of the component coupler and the second measurement subassembly.
Moreover, the measurement system can include a housing that defines a sealed housing chamber that encircles and encloses the measuring assembly and the component coupler, with the device coupler positioned outside the housing. With this design, the rotary measurement system is sealed, it can be relatively inexpensive to manufacture, and it can be relatively easy to integrate into the design of a precision apparatus. As a result thereof, the rotary measurement system is particularly suited for usage in dirty environments.
In one embodiment, the housing includes a housing wall that is positioned between the component coupler and the device coupler. Further, the housing can include a housing bearing that rotatable secures the second measurement subassembly to the housing, while the first measurement subassembly can be fixedly secured to the housing.
As provided herein, the measurement system can be an optical rotary encoder. With this design, one of the measurement subassemblies is an optical disk and the other of the measurement subassemblies is an optical reader.
Further, as provided herein, the coupling assembly can be a magnetic coupler. With this design, one of the couplers includes a magnet and the other of the couplers includes a material that is attracted to the magnet. Thus, the component coupler and the device coupler cooperate to define a magnetic coupler.
Additionally, the present invention is directed to a precision apparatus including a motor that rotates a device, and the measurement system having the device coupler secured to the device.
The present invention is also directed to a method for measuring a rotational position of a device that includes the steps of: (i) providing a housing; (ii) fixedly securing a first measurement subassembly to the housing; (iii) rotatable securing a second measurement subassembly to the housing; (iv) fixedly coupling a component coupler to the second measurement subassembly; and (v) fixedly coupling a device coupler to the device. In this embodiment, the device coupler interacts with the component coupler in a non-contact fashion so that the rotation of the device coupler results in rotation of the component coupler and the second measurement subassembly.
The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:
As provided herein, in certain embodiments, the rotary measurement system 20 is sealed and is uniquely designed to be relatively inexpensive to manufacture, and relatively easy to integrate into the design of the apparatus 10. As a result thereof, the rotary measurement system 20 is particularly suited for usage in dirty environments.
A number of Figures include an orientation system that illustrates an X axis, a Y axis that is orthogonal to the X axis, and a Z axis that is orthogonal to the X and Y axes. It should be noted that these axes can also be referred to as the first, second, and third axes.
The apparatus frame 12 is rigid and supports the other components of the apparatus 10.
The mover 14 is coupled to the object 16 and the rotary measurement system 20. The mover 14 can be any type of actuator. In
The object 16 being rotated can be any type of device. As non-exclusive examples, the object 16 being rotated can be a robotic arm, a wheel of a vehicle, a precision manufacturing tool, or a precision manufacturing tool, or a washer drum in a washing machine appliance.
The control system 18 directs current to the mover 14 and controls the operation of the apparatus 10. For example, the control system 18 can receive rotational position information from the measurement system 20 and can control the mover 14 to accurately position the object 16. For example, the control system 18 can include one or more processors.
The measurement system 20 measures the rotational position and/or rotational rate of a device (e.g. the second output 14B and/or the object 16), and provides rotational position information relating to the rotational position of the device to the control system 18. With this design, in certain embodiments, the mover 14 can be operated in closed-loop fashion. In the embodiment illustrated in
The housing 222 defines a sealed housing chamber 236 that encircles and encloses the measuring assembly 224 and the component coupler 232 of the coupling assembly 230. In one non-exclusive embodiment, the housing 222 is shaped somewhat similar to a rectangular shaped box that includes six, generally flat housing walls 238A-238 (only five are illustrated in
The housing walls 238A-238E can be made of any material that is rigid, non-magnetic, and that does not influence the operation of the coupling assembly 230. Non-exclusive examples of suitable materials for the housing walls 238A-238E include glass, plastics, or metals.
In
The measuring assembly 224 provides the rotational position information. In one embodiment, the measuring assembly 224 is a rotational optical encoder that includes the first measurement subassembly 226 and the second measurement subassembly 228.
In the embodiment illustrated in
In
Additionally, in
With this design, the optical disk 248 rotates relative to the light source 244 and the optical reader 246, and the measuring assembly 224 measures the amount of relative movement and/or rotation rate between the optical disk 248 and the optical reader 246 by counting the encoder marks 352. Alternatively, one or all of the encoder marks 352 can have a unique design that allows the optical reader 246 to specifically identify each of the encoder marks 352. This feature allows the measuring assembly 224 to determine rotational position without counting encoder marks 352.
Additionally, referring back to
The coupling assembly 230 couples the device 214B to the measuring assembly 224. In one embodiment, the component coupler 228 and the device coupler 230 are spaced apart a coupler gap 258 and one of the housing walls 238A is positioned in the coupler gap 258.
In one embodiment, the coupling assembly 230 is a magnetic type coupler. In this embodiment, one of the couplers 232, 234 includes a magnet assembly 260, and the other of the couplers 234, 232 includes an attracted assembly 262. For example, the component coupler 232 can include the magnet assembly 260, and the device coupler 234 can include the attracted assembly 262. Alternatively, the component coupler 232 can include the attracted assembly 262, and the device coupler 234 can include the magnet assembly 260. With both arrangements, the component coupler 232 and the device coupler 234 are coupled together in a non-contact fashion. As a result thereof, rotation of the device coupler 234 results in equal rotation of the component coupler 232 and the second measurement subassembly 228.
The design of the magnet assembly 260 and the attracted assembly 262 can be varied pursuant to the teachings provided herein. In the embodiment illustrated in
In one embodiment, each of the magnets 264 is a permanent magnet. Alternatively, one or more of the magnets 264 can be an electromagnet.
Further, each of the attracted members 266 can be made of a material that is attracted to the magnet 264. Suitable materials for the attracted members 266 include ferromagnetic materials such as iron, nickel, cobalt, and alloys thereof.
While the particular system 20 as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.
