Locomotive wheelslip control system

For inclusion in a propulsion system of a traction vehicle having a plurality of wheels that are subject to slipping with respect to the surface on which the vehicle travels, the system comprising a plurality of adjustable speed electric motors mechanically coupled in driving relationship to separate wheels of the vehicle, a controllable source of electric power the output of which is electrically coupled in energizing relationship to the respective motors, means associated with the source of power for varying the magnitude of its output current or voltage in accordance with a variable control signal, means for deriving a feedback signal representative of the actual current or voltage magnitude, and a plurality of means for respectively sensing the rotational speeds of the separately driven wheels, said control signal being provided by a controller to which the speed sensing means are coupled and which is operative to vary the control signal as necessary to minimize any difference between the feedback signal and a reference signal the value of which normally depends on the value of a variable command signal, improved wheelslip control means comprising:

• a. first means for comparing the rotational speeds of the separately driven wheels of the vehicle and for detecting the highest and lowest speeds, respectively;
• b. second means associated with said first means for providing a reference speed value indicative of the rotational speed of a vehicle wheel that is not slipping;
• c. third means for determining a normally desired maximum difference between the reference speed indicated by said second means and a predetermined one of the speeds detected by said first means;
• d. summing means associated with said first, second and third means for deriving a speed error value representative of the algebraic sum of said predetermined one speed, said reference speed and said maximum difference, said speed error value being zero whenever said one speed has a desired value;
• e. integrating means associated with said summing means and operative when the actual value of said one speed differs from the desired value in a predetermined direction for obtaining a wheelslip correction value that increases at an average rate that is a predetermined function of said speed error value;
• f. additional means associated with said integrating means and operative when the actual value of said one speed does not differ from said desired value in said predetermined direction and said wheelslip correction value is greater than zero for decreasing said correction value at an average rate that is independent of said speed error value;
• and
• g. means associated with said integrating means for reducing the value of said reference signal by an amount corresponding to said correction value.

For inclusion in a propulsion system of a traction vehicle having a plurality of wheels that are subject to slipping with respect to the surface on which the vehicle travels, the system comprising a plurality of adjustable speed electric motors mechanically coupled in driving relationship to separate wheels of the vehicle, a controllable source of electric power the output of which is electrically coupled in energizing relationship to the respective motors, means associated with the source of power for varying the magnitude of its output current or voltage in accordance with a variable control signal, means for deriving a feedback signal representative of the actual current or voltage magnitude, and a plurality of means for respectively sensing the rotational speeds of the separately driven wheels, said control signal being provided by a controller to which the speed sensing means are coupled and which is operative to vary the control signal as necessary to minimize any difference between the feedback signal and a reference signal the value of which normally depends on the value of a variable command signal, improved wheelslip control means comprising:

• a. first means for comparing the rotational speeds of the separately driven wheels of the vehicle and for detecting the highest and lowest speeds, respectively;
• b. second means associated with said first means for providing a reference speed value indicative of the rotational speed of a vehicle wheel that is not slipping;
• c. third means for determining a normally desired maximum difference between the reference speed indicated by said second means and a predetermined one of the speeds detected by said first means;
• d. summing means associated with said first, second and third means for deriving a speed error value representative of the algebraic sum of said predetermined one speed, said reference speed and said maximum difference, said speed error value being zero whenever said one speed has a desired value;
• e. means responsive to said speed error value for deriving a voltage error value that is a predetermined function of said speed error value;
• f. integrating means operative when the actual value of said one speed differs from the desired value in a predetermined direction for obtaining a wheelslip correction value that increases at an average rate that varies with said voltage error value;
• g. memory means effective while said wheelslip correction value is greater than zero for saving a value approximately the same as the value of said reference signal at the time when said integrating means becomes operative, said saved value being substantially constant;
• and
• h. means associated with said integrating means and operative while said memory means is effective for reducing said reference signal value to a level equal to said saved value minus said correction value regardless of the value of said command signal.

For inclusion in a propulsion system of a traction vehicle having a plurality of wheels that are subject to slipping with respect to the surface on which the vehicle travels, the system comprising a plurality of adjustable speed electric motors mechanically coupled in driving relationship to separate wheels of the vehicle, a controllable source o electric power the output of which is electrically coupled in energizing relationship to the respective motors, means associated with the source of power for varying the magnitude of its output current or voltage in accordance with a variable control signal, means for deriving a feedback signal representative of the actual current or voltage magnitude, and a plurality of means for respectively sensing the rotational speeds of the separately driven wheels, said control signal being provided by a controller to which the speed sensing means are coupled and which is operative to vary the control signal as necessary to minimize any difference between the feedback signal and a reference signal the value of which normally depends on the value of a variable command signal, improved wheelslip control means comprising:

• a. first means for comparing the rotational speeds of the separately driven wheels of the vehicle and for detecting the highest and lowest speeds, respectively;
• b. second means for respectively deriving the rates of change of rotational speeds of said separately driven wheels;
• c. third means for comparing said rates of change and for detecting the highest one;
• d. bistable means operative from a reset state to a set state in response to the highest rate increasing to at least a predetermined pickup level;
• e. wheelslip detection means for detecting the number of said separately driven wheels that are slipping, as indicated by excessively high derivatives of the rates of change derived by said second means;
• f. reference speed indicating means associated with said first means for providing a reference speed value that normally varies with the rotational speed of a vehicle wheel that is not slipping but that will not change appreciably if either the number of slipping wheels is above a predetermined limit or said bistable means is in its set state;
• g. means for determining a normally desired maximum difference between the reference speed indicated by said second means and a predetermined one of the speeds detected by said first means;
• h. summing means for deriving a speed error value representative of the algebraic sum of said predetermined one speed, said reference speed and said maximum difference, said speed error value being zero whenever said one speed has a desired value;
• j. means responsive to said speed error value for deriving a voltage error value that is a predetermined function of said speed error value;
• k. integrating means operative when the actual value of said one speed differs from the desired value in a predetermined direction for obtaining a wheelslip correction value that increases at an average rate that varies with said voltage error value;
• and
• m. means associated with said integrating means for reducing the value of said reference signal by an amount corresponding to said correction value.

For inclusion in a propulsion system of a traction vehicle having a plurality of wheels that are subject to slipping with respect to the surface on which the vehicle travels, the system comprising a plurality of adjustable speed electric motors mechanically coupled in driving relationship to separate wheels of the vehicle, a controllable source of electric power the output of which is electrically coupled in energizing relationship to the respective motors, means associated with the source of power for varying the magnitude of its output current or voltage in accordance with a variable control signal, means for deriving a feedback signal representative of the actual current or voltage magnitude, and a plurality of means for respectively sensing the rotational speeds of the separately driven wheels, said control signal being provided by a controller to which the speed sensing means are coupled and which is operative to vary the control signal as necessary to minimize any difference between the feedback signal and a reference signal the value of which normally depends on the value of a variable command signal, improved wheelslip control means comprising:

• a. first means for comparing the rotational speeds of the separately driven wheels of the vehicle and for detecting the highest and lowest speeds, respectively;
• b. second means associated with said first means for providing a reference speed value indicative of the rotational speed of a vehicle wheel that is not slipping;
• c. third means for determining a normally desired maximum difference between the reference speed indicated by said second means and a predetermined one of the speeds detected by said first means;
• d. summing means associated with said first, second and third means for deriving a speed error value representative of the algebraic sum of said predetermined one speed, said reference speed and said maximum difference, said speed error value being zero whenever said one speed has a desired value;
• e. wheelslip detection means for detecting the number of separately driven wheels that are slipping, as indicated by excessively high second derivatives of the rotational speeds of the individual wheels;
• f. additional means coupled to said wheelslip detection means for determining whether or not the number of slipping wheels is above a predetermined limit;
• g. means associated with said additional means and said summing means and effective when the number of slipping wheels is above said limit to change the desired value of said one speed by a variable amount that increases with the length of time that the number of slipping wheels is above said limit, said desired-value change tending to increase said speed error value in a positive direction;
• h. means associated with said summing means and operative when said speed error value is positive for obtaining a wheelslip correction value that is a predetermined function of said speed error value;
• and
• j means responsive to said wheelslip correction value for reducing the value of said reference signal by an amount corresponding to said correction value.

For inclusion in a propulsion system of a traction vehicle having a plurality of wheels that are subject to slipping with respect to the surface on which the vehicle travels, the system comprising a plurality of adjustable speed electric motors mechanically coupled in driving relationship to separate wheels of the vehicle, a controllable source of electric power the output of which is electrically coupled in energizing relationship to the respective motors, means associated with the source of power for varying the magnitude of its output current or voltage in accordance with a variable control signal, means for deriving a feedback signal representative of the actual current or voltage magnitude, and a plurality of means for respectively sensing the rotational speeds of the separately driven wheels, said control signal being provided by a controller to which the speed sensing means are coupled and which is operative to vary the control signal as necessary to minimize any difference between the feedback signal and a reference signal the value of which normally depends on the value of a variable command signal, improved wheelslip control means comprising:

• a. first means for comparing the rotational speeds of the separately driven wheels of the vehicle and for detecting the highest and lowest speeds, respectively;
• b. second means associated with said first means for providing a reference speed value indicative of the rotational speed of a vehicle wheel that is not slipping;
• c. third means for determining a normally desired maximum difference between the reference speed indicated by said second means and a predetermined one of the speeds detected by said first means;
• d. summing means associated with said first, second and third means for deriving a speed error value representative of the algebraic sum of said predetermined one speed, said reference speed and said maximum difference, said speed error value being zero whenever said one speed has a desired value;
• e. means for respectively deriving the rates of change of rotational speeds of the separately driven wheels of the vehicle, for comparing said rates, and for detecting the lowest one;
• f. bistable means operative from a reset state to a set state in response to the lowest rate increasing to at least a predetermined pickup level;
• g. means associated with said summing means and effective when said bistable means is in its set state to change the desired value of said one speed by a variable amount that increases with the length of time that said bistable means is in its set state, said desired-value change tending to increase said speed error value in a positive direction;
• h. means associated with said summing means and operative when said speed error value is positive for obtaining a wheelslip correction value that is a predetermined function of said speed error value;
• and
• j. means responsive to said wheelslip correction value for reducing the value of said reference signal by an amount corresponding to said correction value.

For inclusion in a propulsion system of a traction vehicle having a plurality of wheels that are subject to slipping with respect to the surface on which the vehicle travels, the system comprising a plurality of adjustable speed electric motors mechanically coupled in driving relationship to separate wheels of the vehicle, a controllable source of electric power the output of which is electrically coupled in energizing relationship to the respective motors, means associated with the source of power for varying the magnitude of its output current or voltage in accordance with a variable control signal, means for deriving a feedback signal representative of the actual current or voltage magnitude, and a plurality of means for respectively sensing the rotational speeds of the separately driven wheels, said control signal being provided by a controller to which the speed sensing means are coupled and which is operative to vary the control signal as necessary to minimize any difference between the feedback signal and a reference signal the value of which normally depends on the value of a variable command signal, improved wheelslip control means comprising:

• a. first means for comparing the rotational speeds of the separately driven wheels of the vehicle and for detecting the highest and lowest speeds, respectively;
• b. second means associated with said first means for providing a reference speed value indicative of the rotational speed of a vehicle wheel that is not slipping;
• c. third means for determining a normally desired maximum difference between the reference speed indicated by said second means and a predetermined one of the speeds detected by said first means;
• d. fourth means for respectively deriving the rates of change of rotational speeds of the separately driven wheels of the vehicle;
• e. fifth means associated with said fourth means for comparing said rates of change and for providing a rate value representative of the highest rate of change;
• f. bistable means operative from a reset state to a set state in response to said rate value increasing to at least a predetermined pickup level;
• g. first summing means associated with said first, second and third means for deriving a speed error value representative of the algebraic sum of said predetermined one speed, said reference speed and said maximum difference, said speed error value being zero whenever said one speed has a desired value;
• h. integrating means associated with said first summing means and operative when the actual value of said one speed differs from the desired value in a predetermined direction for obtaining a first variable value that increases at an average rate that is a predetermined function of said speed error value;
• j. additional means effective when said bistable means is in its set state for obtaining a second variable value that depends on the value of said feedback signal;
• k. second summing means associated with said integrating means and said additional means for deriving a wheelslip correction value that varies with the sum of said first and second variable values;
• and
• m. means responsive to said wheelslip correction value for reducing the value of said reference signal by an amount corresponding to said correction value.

For inclusion in a propulsion system of a traction vehicle having a plurality of wheels that are subject to slipping with respect to the surface on which the vehicle travels, the system comprising a plurality of adjustable speed electric motors mechanically coupled in driving relationship to separate wheels of the vehicle, a controllable source of electric power the output of which is electrically coupled in energizing relationship to the respective motors, means associated with the source of power for varying the magnitude of its output current or voltage in accordance with a variable control signal, means for deriving a feedback signal representative of the actual current or voltage magnitude, and a plurality of means for respectively sensing the rotational speeds of the separately driven wheels, said control signal being provided by a controller to which the speed sensing means are coupled and which is operative to vary the control signal as necessary to minimize any difference between the feedback signal and a reference signal the value of which normally depends on the value of a variable command signal, improved wheelslip control means comprising:

• a. first means for comparing the rotational speeds of the separately driven wheels of the vehicle and for detecting the highest and lowest speeds, respectively;
• b. second means associated with said first means for providing a reference speed value indicative of the rotational speed of a vehicle wheel that is not slipping;
• c. third means for determining a normally desired maximum difference between the reference speed indicated by said second means and a predetermined one of the speeds detected by said first means;
• d. fourth means for respectively deriving the rates of change of rotational speeds of the separately driven wheels of the vehicle;
• e. fifth means associated with said fourth means for comparing said rates of change and for providing a rate value representative of the highest rate of change;
• f. bistable means operative from a reset state to a set state in response to said rate value increasing to at least a predetermined pickup level;
• g. first summing means associated with said first, second and third means for deriving a speed error value representative of the algebraic sum of said predetermined one speed, said reference speed and said maximum difference, said speed error value being zero whenever said one speed has a desired value;
• h. integrating means associated with said first summing means and operative when the actual value of said one speed differs from the desired value in a predetermined direction for obtaining a first variable value that increases at an average rate that is a predetermined function of said speed error value;
• j. additional means associated with said fifth means and effective when said bistable means is in its set state for obtaining a second variable value that depends on said rate value;
• k. second summing means associated with said integrating means and said additional means for deriving a wheelslip correction value that varies with the sum of said first and second variable values;
• and
• m. means responsive to said wheelslip correction value for reducing the value of said reference signal by an amount corresponding to said correction value.