Abstract:
A method and an electrical drive assembly  10  which operates in accordance with the method. Particularly, the drive assembly  10  includes a diagnostic portion  18  which compares a voltage signal which is communicated to an electrical machine  28  and a voltage signal which is selected by use of a desired torque command signal  33  and which provides a diagnostic of the electrical drive assembly  10  based upon the comparison, effective to provide a positive indication to a user of the drive assembly.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to a diagnostic method for determining whether an electric drive assembly is producing a desired amount of torque and to an electric drive assembly which incorporates the method and more particularly, to an electric drive assembly which compares a pair of signals or values in order to determine whether the assembly is producing a desired amount of torque.  
           [0003]    2. Background of the Invention  
           [0004]    Electric drive assemblies are utilized in a wide variety of applications requiring the selective production of torque. Examples of such applications include, but are not limited to, manufacturing or producing an item or causing selective propulsion. It is desirable to ensure or ascertain whether these electric drive assemblies are desirably providing a required amount of torque.  
           [0005]    One strategy to increase the likelihood that a desired amount of torque will be produced by an electric drive assembly includes the use of an electrical current regulator which receives a measured signal which was previously communicated to the electric machine or torque producer and which represents the torque requested of the electric machine. Particularly, the current regulator subtracts this received signal from a second signal which represents the currently desired or commanded torque. The regulator uses this difference or modifier to produce a voltage signal which is used to create a torque control signal which is communicated to the electric machine, effective to cause the electric machine to produce the certain amount of desired torque. The current regulator therefore tends to cause the electric machine to produce a desired amount of torque.  
           [0006]    While this strategy does reduce the likelihood of the production of undesired torque, it does not entirely eliminate the possibility of undesired operation. This strategy also does not ensure that such undesired operation will be recognized in a timely manner by an operator or user of the electric drive assembly since the electrical current regulator does not identify, or make known to the user, the nature of the operation of the electric drive assembly.  
           [0007]    The present invention allows for a relatively efficient determination to be made of the amount of torque which is produced by an electric drive assembly and for the selective creation of a positive indication or diagnostic feedback signal which is indicative of the operational status of the electric drive assembly, thereby allowing an operator or a user of the electric drive assembly to take some action in the event that the electric drive assembly is producing an undesirable amount of torque.  
         SUMMARY OF INVENTION  
         [0008]    An electric drive assembly is provided having certain features/attributes that overcome some or all of the previously delineated drawbacks of prior drive assemblies.  
           [0009]    The present invention provides a method for quickly and efficiently determining whether an electric drive assembly is providing a desired amount of torque.  
           [0010]    In addition, an electric drive assembly which selectively produces a certain amount of torque and which further provides a positive indication or a positive feedback signal when the assembly is producing torque in an undesired manner is provided.  
           [0011]    According to the teachings of one non-limiting embodiment of the present invention, an electric drive assembly is provided. Particularly, the electric drive assembly includes a torque generator; an inverter assembly which is coupled to the torque generator; a current regulator which is coupled to the inverter assembly; and a controller which is coupled to the current regulator, wherein the controller receives a torque request signal and, in response to the received torque request signal, the controller selects a certain value and generates a signal to the inverter assembly which is effective to cause the inverter assembly to produce a voltage signal having a certain amplitude attribute and a certain phase angle attribute, the controller further compares at least one of the attributes of the voltage signal with the selected certain value and, based upon the comparison, generates a signal indicative of an existence of undesired torque generation.  
           [0012]    According to the teachings of a second non-limiting embodiment of the present invention, an electric drive assembly is provided and includes a torque map portion which receives a certain torque request and which uses the certain torque request to produce a certain electrical current value; a model portion which receives the certain torque request and which uses the received torque request to produce a certain voltage value; a current regulator which receives an electrical current signal having a value which is substantially similar to the electrical current value and which, in response to the receipt of the certain electrical current signal, produces a second voltage signal having a certain second value; and a diagnostic portion which is coupled to the current regulator and to the model portion and which compares the certain voltage value with the second voltage value and which determines the existence of a predetermined state of operation based upon the comparison.  
           [0013]    According to a third non-limiting aspect of the present invention, a method for determining the existence of a certain state of operation of an electric drive assembly of the type which receives a certain torque request and which uses the received certain torque request to produce a voltage command is provided. Particularly, the method includes the steps of associating the torque request with a second voltage command; comparing the produced voltage command with the second voltage command; ascertaining the existence of a certain operational state of the electric drive assembly based upon said comparison; and automatically deactivating the electric drive assembly upon the ascertained existence of the certain operational state.  
           [0014]    These and other features and advantages of the present invention will become apparent from a reading of the following detailed description of the preferred embodiment of the invention and by reference to the following drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]    [0015]FIG. 1 is a block diagram of an electric drive assembly which is made in accordance with the teachings of the preferred embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0016]    Referring now to FIG. 1, there is shown an electric drive assembly  10  which is made in accordance with the teachings of the preferred embodiment of the invention. Particularly, the electric drive assembly  10  includes a controller  12  which is operable under stored program control and which may comprise, by way of example and without limitation, a commercially available processor assembly. The controller  12  includes a torque map portion  14 , a model portion  16 , and a check or consistency/diagnostic portion  18 . It should be appreciated that each of these portions  14 ,  16 ,  18  may be implemented within software and may be operatively resident within the controller  12  and that, in one non-limiting embodiment, portion  18  may reside outside of the controller  12 . It should be further appreciated that the controller  12  may be physically and communicatively coupled to a source of energy (not shown) and is effective, according to the methodology of the invention, to selectively cause the energy source to output energy along output bus  50 .  
         [0017]    The electric drive assembly  10  further includes an electrical current regulator  20 , a pulse width modulator or modulation assembly  22 , an inverter  24  which is coupled to the pulse width modulation assembly  22 , by bus  25 , and an electric machine or torque producer  28  which is coupled to the inverter  24  and to the controller  12  by bus  27 . The machine  28  includes a selectively movable shaft or member  29  and, in one non-limiting embodiment of the invention, may comprise a conventional motor assembly. Portions  14  and  16  are communicatively coupled to the input bus  31  and inverter  24  and pulse width modulation assembly  22  may cooperatively compromise an “inverter assembly”.  
         [0018]    Particularly, in operation, member  29  selectively rotates, thereby producing torque, when the electric machine  28  receives electrical power or is energized or activated by the receipt of electrical energy which is communicated to the electrical machine  28  by use of the bus  27 . As is shown, the electrical current regulator  20  is physically and communicatively coupled to the pulse width modulator  22  by bus  52  and is physically and communicatively coupled to the controller  12  by the bus  50 . The controller  12  is further adapted to receive a torque request signal  33  by use of the bus  31  and is physically and electrically coupled to the bus  52  through the diagnostic or feedback signal generation portion  18 . In one non-limiting embodiment of the invention, assembly  10  may not include the machine  28 , but rather is selectively operable and attachable to a variety of torque producing machines.  
         [0019]    Particularly, the torque map portion  14  comprises a table which uniquely associates desired or requested amounts of torque, such as and without limitation the amount of torque represented by signal  33  which appears on bus  31 , with a certain respective amount of electrical current needed by (e.g., needed to be communicated to) the electric machine  28  to produce these respective desired amounts of torque (e.g., each stored desired amount of torque has a respective amount of electrical current which is uniquely associated with it). In one non-limiting embodiment, this table may be created by testing or calibrating the electric machine  28 . A received torque command signal  33  having a torque value which is not resident within the torque map table is used to select an electrical current value by the mathematical process of interpolation. That is, the electrical current values associated with the nearest higher and lower actually stored torque values are used to interpolatively select an electrical current value for the received signal  33 . Alternatively, the stored torque value which is “nearest” to the value of the input torque signal  33  is selected in the torque map portion  14  and the associated electrical current value of this selected and stored torque value is used in the methodology which is delineated below.  
         [0020]    The model portion  16  comprises a table which uniquely associates desired or requested amounts of torque, such as and without limitation the amount of torque represented by signal  33 , with a certain respective amount of voltage which is required to be output from the current regulator  20  in order to allow the electrical machine  28  to produce the respective desired amounts of torque (e.g., each stored desired amount of torque has a respective amount of voltage which is uniquely associated with it). In one non-limiting embodiment, this table may be created by testing or calibrating the current regulator  20  and the electric machine  28 . A torque request signal, such as that represented by signal  33 , having a value which is not resident within the model portion  16 , is used to select a voltage signal by the mathematical process of interpolation. That is, the voltage values associated with nearest higher and lower actually stored torque values are used to interpolatively select a voltage value for the received signal  33 . Alternatively, the stored torque value which is “nearest” to the value of the input torque signal  33  is selected in the model portion  16  and the associated voltage of the selected and stored torque value is used in the methodology which is delineated below.  
         [0021]    In operation, the signal  33  which specifies a certain amount of desired torque is input and communicated to the controller  12  by a user or operator of the electric drive assembly  10 . The input signal  33  is then used by the controller  12  to access the torque map portion  14 , thereby selecting a certain amount or value of electrical current which is necessary to be communicated to the electrical machine  28 , by the use of bus  27 , to cause the electrical machine  28  to produce the desired amount of torque. The torque request signal is also input into the model portion  16  and the model portion  16  uses the received torque request signal  33  to select a voltage value and/or generate a voltage signal having this value which is required to be output from the current regulator  20 , necessary to cause the desired amount of torque to be produced.  
         [0022]    A current signal having a value which is equal to the current value selected from the torque map portion  14  is then provided from the energy source (not shown) and may be communicated to the current regulator  20 , by use of bus  50 . The current regulator  20  then uses the received electrical current signal to produce a voltage signal and communicates the voltage signal to the pulse width modulator  22  by the use of bus  52 . The pulse width modulator  22  then modulates the received voltage signal and communicates the modulated voltage signal to the inverter  24 , by the use of bus  25 .  
         [0023]    The inverter  24  then applies the received voltage signal to the electrical machine  28 , by the use of bus  27 , thereby producing an electrical current signal, effective to cause the electrical machine  28  to produce a desired amount of torque. The electrical current signal, which is output from the inverter  24 , is also communicated to the current regulator  20 , by the bus  27 , thereby allowing the current regulator  20  to ensure that the next received electrical current signal is modified by this signal, thereby efficiently correcting for any undesired torque production from the electric machine  28 . Additionally, the voltage signal which is produced by the current regulator  20  is communicated to the diagnostic portion  18 , by the use of bus  52 , where its value is compared with the voltage value which was identified/produced from the model portion  16 . Should these compared voltage values differ by at least a certain amount, a diagnostic signal is generated by the controller  12  to a selectively energizable or activatable positive feed back assembly, effective to activate the positive feed back assembly and to notify an operator or user of the assembly  10  that a certain operational state (e.g., a state in which an undesired amount of torque is being produced) is occurring within the assembly  10 . Examples of such a positive feed back assembly may include, by way of example and without limitation, a selectively energizable light assembly and/or a selectively energizable audio assembly. Additionally or alternatively, controller  12  may also automatically (i.e., without user intervention) deactivate the electric machine  28  when the assembly  10  resides in such an operational state. In one non-limiting embodiment, this certain amount exists where the difference between the voltage value identified from the model portion  16  and the voltage value of the signal produced by the current regulator  20  is equal to about 10% of the value identified or selected by the model portion  16 . Other threshold values may be alternatively used. In this manner, the user is given a positive indication of the production of an undesirable amount of torque from the machine  28  and the electric machine  28  may be automatically (e.g., without user intervention) deactivated. One non-limiting method which may be used to automatically deactivate the electric machine  28  is to cause the controller  22  to prevent electrical energy from being delivered to the electric machine  28  by the use of bus  50 .  
         [0024]    It is to be understood that the present invention is not limited to the exact construction or method which has been delineated above, but that various changes and modifications may be made without departing from the spirit and the scope of the inventions as are further delineated within the following claims. Further, in other non-limiting embodiments, the data which is resident within the model portion  16  may alternatively comprises voltage phase angle type data and the data which is obtained from the current regulator  20  and communicated to the model portion  16  may also alternatively comprise voltage angle data. Further, in yet another non-limiting embodiment, the controller  12  may ascertain the production of an undesired amount of torque by identifying certain undesired harmonic components or a certain amount of imbalance of the assembly  18  (e.g., by the use of vibration sensors (not shown)), thereby obviating the need for the model portion  16 . In this non-limiting “unbalance detection” embodiment, the torque map portion  14  may still be utilized in order to determine the current command required for the current regulator  20 .