Patent ID: 8073602

Claim:
A method for controlling an electro-mechanical transmission mechanically coupled to first and second electric machines to transmit power to an output member, the method comprising: determining motor torque constraints for the first and second electric machines; determining battery power constraints for an electrical energy storage device electrically connected to the first and second electric machines; determining a range for an additional torque input to the electro-mechanical transmission; determining a preferred output torque to the output member of the electro-mechanical transmission that is achievable within the motor torque constraints, is achievable within the range of the additional torque input, and is based upon the battery power constraints; and controlling operation of the electro-mechanical transmission and the first and second electric machines to achieve the preferred output torque to the output member of the electro-mechanical transmission; wherein determining the preferred output torque to the output member of the electro-mechanical transmission comprises: formulating mathematical equations representing the motor torque constraints comprising maximum and minimum motor torque constraints for the first and second electric machines; formulating mathematical equations representing maximum and minimum battery power constraints; formulating a mathematical equation representing the output torque; formulating mathematical equations representing the range for the additional torque input; transforming the mathematical equations representing the maximum and minimum battery power constraints to equations of concentric circles having respective radii; transforming the mathematical equations representing the maximum and minimum motor torque constraints for the first and second electric machines to equations comprising lines; transforming the mathematical equations representing the range for the additional torque input to equations comprising lines; transforming the mathematical equation representing the output torque to an equation comprising a line; determining at least one transformed achievable output torque based upon the transformed mathematical equations representing the maximum and minimum motor torque constraints for the first and second electric machines, the maximum and minimum battery power constraints, and the range for the additional torque input; determining a transformed achievable output torque corresponding to the at least one transformed achievable output torque; and retransforming the transformed achievable output torque.