Control system for electric motor for driving electric vehicle

A control system for an electric motor for driving a brushless DC electric vehicle including a rotor having a field system and a stator having armature coils of n phases (n is two or more integers) while an output of said electric motor is controlled on an accelerator opening degree corresponding to a displacement quantity of an accelerator operation member, said control system comprising an acceleration sensor to output an acceleration signal having a magnitude corresponding to said accelerator opening degree by detecting said accelerator opening degree;

• rotational speed detection means to detect a rotational speed of said electric motor;
• n position sensors to generate an output having a level varying whenever a polarity of magnetic poles directly or indirectly detected by said magnetic poles of said rotor relative to armature coils of n phases of said stator, respectively changes;
• a switch circuit provided between a DC power supply and said armature coils to switch the phase of the armature coil through which a drive current flows from said DC power supply;
• steady-state-time drive current control means having duty factor arithmetical operation means to arithmetically operate a duty factor of said drive current for said acceleration signal and switch control means to control said switch circuit so that there flows through the armature coil of phase determined in accordance with an output of said position sensors the drive current of PWM waveform intermittent in the duty factor arithmetically operated by said duty factor arithmetical operation means whereby said rotor rotates;
• lock state judgment means to judge that said electric motor is in the lock state when the state where said rotational speed detected by said rotational speed detection means is equal to or less than a set lock start rotational speed while said accelerator opening degree detected from said acceleration signal is equal to or more than a set lock judgment opening degree continues for a set lock start judgment time and to judge that said lock state is released when the state where said accelerator opening degree is less than said lock judgment opening degree or the state where said rotational speed is equal to or more than a lock release rotational speed set at a value higher than said lock start rotational speed continues for a set lock release judgment time;
• and lock-time drive current control means to perform a drive current limit control in which said duty factor of said drive current is reduced from a value arithmetically operated by said duty factor arithmetical operation means to a lock-time limit duty factor so that the maximum value of said drive current is limited to the value equal to or less than said lock-time limit value when it is judged by said lock state judgment means that the electric motor is in the lock state and to release said drive current limit control whereby said duty factor of said drive current is increased from said lock-time limit value to said value determined by said duty factor arithmetical operation means when it is judged that said lock state is released.

A control system for an electric motor for driving a brushless DC electric vehicle including a rotor having a field system and a stator having armature coils of n phases (n is two or more integers) while an output of said electric motor is controlled on an accelerator opening degree corresponding to a displacement quantity of an accelerator operation member, said control system comprising an acceleration sensor to output an acceleration signal having a magnitude corresponding to said accelerator opening degree by detecting said accelerator opening degree;

• rotational speed detection means to detect a rotational speed of said electric motor;
• n position sensors to generate an output having a level varying whenever a polarity of magnetic poles directly or indirectly detected by said magnetic poles of said rotor relative to armature coils of n phases of said stator, respectively changes;
• a switch circuit provided between a DC power supply and said armature coils to switch the phase of the armature coil through which a drive current flows from said DC power supply;
• steady-state-time drive current control means having duty factor arithmetical operation means to arithmetically operate a duty factor of said drive current on said acceleration signal and switch control means to control said switch circuit so that there flows through the armature coil of phase determined in accordance with an output of said position sensors the drive current of PWM waveform intermittent in the duty factor arithmetically operated by said duty factor arithmetical operation means whereby said rotor rotates;
• rotation state judgment means to judge whether said electric motor rotates in the forward direction or not by using the difference of a combination of output states of said n position sensors between the forward rotation of said electric motor and the reverse rotation thereof;
• lock state judgment means to perform every predetermined time the judgment that said electric motor is in the lock state when the state where it is judged by said rotation state judgment means that said electric motor rotates in the forward direction and said rotational speed is equal to or less than a set lock start rotational speed while said accelerator opening degree detected from said acceleration signal is equal to or more than a set lock judgment opening degree continues for a set lock start judgment time or when it is judged that said electric motor does not rotate in the forward direction while said accelerator opening degree is equal to or more than said lock judgment opening degree continues for a set lock start judgment time and the judgment that said lock state is released when the state where said accelerator opening degree is less than said lock judgment opening degree or the state where said rotational speed is equal to or more than a lock release rotational speed set at a value higher than said lock start rotational speed continues for a set lock release judgment time;
• and lock time drive current control means to perform a drive current limit control in which the maximum value of said drive current is reduced to a value equal to or less than a lock-time limit value when it is judged that the electric motor is in the lock state and to release said drive current limit control when it is judged that said lock state is released.