Electricity: motive power systems – Constant motor current – load and/or torque control – Control of motor load or device driven
Reexamination Certificate
2000-03-22
2001-10-09
Bonck, Rodney H. (Department: 3681)
Electricity: motive power systems
Constant motor current, load and/or torque control
Control of motor load or device driven
C318S034000, C318S139000, C477S003000, C180S065230, C180S065600
Reexamination Certificate
active
06300735
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to an electromechanical transmission, and more particularly, to a control for a two degree of freedom, multiple member electromechanical transmission wherein output torque commands received are implemented within power and torque limits for electric machines used for controlling the transmission output.
BACKGROUND ART
An electromechanical transmission typically includes a planetary gearing arrangement having, for example, three planetaries, and multiple members connected respectively to an engine, multiple electric machines, and an output. The electric machines are each typically operable in a generator mode or a motor mode and are electrically linked. Sometimes the electrical circuitry additionally includes a power source and/or a storage device such as one or more batteries. By the term two degree of freedom transmission, it is generally meant that two unique parameters are needed to positively control the transmission output.
When controlling a two degree of freedom electromechanical transmission, a problem to be overcome is how to maximize the dynamic response of the transmission to input commands such as an operator input, changing load conditions and/or changing environmental conditions such as grade and the like, while also maximizing electrical efficiency, without exceeding torque and power limits for the electrical machines which change with speed. Particularly in this regard, it is desired to maintain a stable voltage over the electrical link between the electrical machines as much as possible over the range of operation of the transmission.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention a control for an electromechanical transmission including a planetary gearing mechanism including an input member adapted for connection to an engine, a member connected to a first electric machine operable as a motor or a generator, a member connected to a second electric machine operable as a motor or a generator, and an output member, the first and second electric machines and the members connected thereto being respectively rotatable for controlling a torque acting on the output member is disclosed. The control includes a first controller for controlling the rotation of the first electric machine and a second controller for controlling the rotation of the second electric machine, the first and second controllers being connected in electrical communication by a conductive link and controllable by first and second torque command signals, respectively, sensors for sensing rotational speeds of the first and second electric machines, respectively, and a transmission controller operable for generating and outputting the first and second torque command signals to the controllers corresponding to a desired torque value for the output member, by determining first and second torque values for the first and second command signals, respectively, without exceeding predetermined torque limits for the electric machines and while maintaining an electrical parameter of the conductive link within a desired range.
In another aspect of this invention, a method for a method for controlling a torque acting on an output member of a transmission having an input member connected to an engine, a member connected to a first electric machine operable as a motor or a generator, and a member connected to a second electric machine operable as a motor or a generator, the first and second electrical machines being controlled by controllers connected in electrical communication by a conductive link is disclosed. The method includes the steps of providing a desired torque value for the output and a corresponding electrical parameter value for the conductive link, calculating an initial torque command value T
EC1
for controlling the first electric machine and an initial torque value T
EC2
for controlling the second electric machine, based on a speed N
1
for the first electrical machine, a speed N
2
for the second electrical machine and a value for the electrical parameter, and comparing the initial torque values T
EC1
and T
EC2
to predetermined limit values L
1
and L
2
, respectively, and if the initial torque values T
EC1
or T
EC2
are less than or equal to the limit values L
1
and L
2
, respectively, then outputting the initial torque values T
EC1
and T
EC2
to the controllers.
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Bonck Rodney H.
Caterpillar Inc.
Ho Ha
Kercher Kevin M.
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