In recent years, advances in technology, as well as ever-evolving tastes in style, have led to substantial changes in the design of automobiles. One of the changes involves the complexity of the electrical systems within automobiles, particularly alternative fuel (or propulsion) vehicles that utilize voltage supplies, such as hybrid and battery electric vehicles. Such alternative fuel vehicles typically use one or more electric motors, often powered by batteries, perhaps in combination with another actuator, to drive the wheels.
Such vehicles often use two separate voltage sources, such as a battery and a fuel cell, to power the electric motors that drive the wheels. Power electronics (or power electronics systems), such as direct current-to-direct current (DC/DC) converters, are typically used to manage and transfer the power from the two voltage sources. Also, due to the fact that alternative fuel automobiles typically include only direct current (DC) power supplies, direct current-to-alternating current (DC/AC) inverters (or power inverters) are also provided to convert the DC power to alternating current (AC) power, which is generally required by the motors.
An important component in the control of power electronics is feedback provided by current sensors which indicate the amount of current actually flowing through the windings in the electric motor, as this feedback is used to optimize efficiency and torque regulation. Any errors associated with the current sensor interface significantly impacts torque regulation. Additionally, Hall Effect Sensors are sometimes used as these current sensors and often experience linearity error, output accuracy error, hysteresis error, and zero current error. Zero current offset may account for a significant portion of the total current sensing error and may be the result of offset from the sensors, circuit interface offset, power supply offset, analog-to-digital channel offset, operating temperature changes, and external noise.
Accordingly, it is desirable to provide an improved system and method for controlling an electric motor which provides at least partially cancellation of such current sensing errors. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.
USPTO Backgrounds
USPTO Backgrounds