Vehicle body speed estimation method and vehicle body speed estimation apparatus

A vehicle body speed estimation method applied to a four-wheel drive vehicle, the vehicle body speed estimation method comprising:

• acquiring an estimated vehicle body speed based on wheel speeds or a longitudinal acceleration of the vehicle;
• determining whether an operation condition that includes at least a condition that the estimated vehicle body speed is higher than an operation determination speed is satisfied;
• performing torque limitation to reduce a torque of a portion of wheels of the vehicle when the operation condition is satisfied;
• determining whether a stop condition that includes a condition that the estimated vehicle body speed is lower than or equal to a stop determination speed or a condition that a duration of a state where a wheel acceleration of the portion of the wheels is higher than zero is longer than or equal to a set period of time;
• stopping the torque limitation when the stop condition is satisfied;
• and
• determining whether a wheel slip is occurring;
• wherein the operation condition includes at least a condition that the wheel slip is occurring and a condition that the estimated vehicle body speed is higher than the operation determination speed, and
• wherein the determining whether the wheel slip is occurring includes:
• acquiring a first estimated vehicle body speed based on the wheel speeds;
• calculating a second estimated vehicle body speed based on an integral of a sum of the longitudinal acceleration and an offset;
• determining whether a slip determination condition that includes at least a condition that the first estimated vehicle body speed is higher than the second estimated vehicle body speed is satisfied;
• and
• determining that the wheel slip is occurring when the slip determination condition is satisfied.

A vehicle body speed estimation apparatus applied to a four-wheel drive vehicle, the vehicle body speed estimation apparatus comprising one or plurality of processors, wherein the one or plurality of processors is programmed to:

• acquire an estimated vehicle body speed based on wheel speeds or a longitudinal acceleration of the vehicle;
• determine whether an operation condition that includes at least a condition that the estimated vehicle body speed is higher than an operation determination speed is satisfied;
• perform torque limitation to reduce a torque of a portion of wheels of the vehicle when the operation condition is satisfied;
• determine whether a stop condition that includes a condition that the estimated vehicle body speed is lower than or equal to a stop determination speed or a condition that a duration of a state where a wheel acceleration of the portion of the wheels is higher than zero is longer than or equal to a set period of time;
• stop the torque limitation when the stop condition is satisfied;
• and
• determine whether a wheel slip is occurring;
• wherein the operation condition includes at least a condition that the wheel slip is occurring and a condition that the estimated vehicle body speed is higher than the operation determination speed, and
• wherein the one or plurality of processors is further programmed to:
• acquire a first estimated vehicle body speed based on the wheel speeds;
• calculate a second estimated vehicle body speed based on an integral of a sum of the longitudinal acceleration and an offset;
• determine whether a slip determination condition that includes at least a condition that the first estimated vehicle body speed is higher than the second estimated vehicle body speed is satisfied;
• and
• determine that the wheel slip is occurring when the slip determination condition is satisfied.