Field of the Invention

The present invention relates to the calculation method of the maximum available torque that can be applied by the system and operating conditions in electric and hybrid vehicle applications, within the limits determined as motor and motor driver temperature, battery current and voltage information, output power, motor line current, acceleration limit and start up condition.

State of the Art

In electric and hybrid vehicle applications, it is important to apply the maximum torque that can be applied within the limits determined by the system and operating conditions without impairing driving comfort and to return the full torque capacity when the limiting factor is removed.

During the research conducted in the state of the art, applications regarding torque limiting applications in electric and hybrid vehicles were encountered.

The application numbered US5446362 concerns the calculation of motor temperature by measuring motor ambient temperature and air pressure. Torque limit and fan speed requirements are determined using the calculated estimated motor temperature information.

The application numbered US6831429 relates to the determination of torque and power limits by using the electrical parameters of the motor (resistance, inductance, magnetic flux, etc.) and battery information (voltage, current, internal resistance, etc.).

In the application numbered US20140021898A1 , the limitation is carried out by using the motor speed and temperature parameters.

In the application numbered US20180273019, it is mentioned that torque limitation is applied in order to plan the battery energy in hybrid vehicles. There is also the step of adjusting the torque limitation depending on other system limits. System limits can be instantaneous motor torque limits and battery power limits without limitation. Motor mechanical limits may depend on motor temperature and inverter voltage, while battery limits may depend on battery temperature, state of charge and battery health.

In the application numbered US20110130904, torque limitation is applied for protection purposes by considering the operating conditions of the power transmission system components. Said limits can be motortemperature, motor speed, voltage and battery.

In the application numbered CN111740673, it is explained that torque limitation is made considering the motorand driver temperature.

In the aforementioned applications in the state of the art, the torque limit is determined by using at most two of the motor temperature, battery information and motor speed data. However, it is important to consider the acceleration limiting and start up condition in terms of driving comfort and safety. In the state of the art, acceleration limiting and start up conditions are not taken into account in the torque calculation process in electric vehicle applications.

As a result, due to the abovementioned disadvantages and the insufficiency of the current solutions regarding the subject matter, a development is required to be made in the relevant technical field.

Aim of the Invention

The main aim of the invention is to calculate the maximum torque that can be applied to provide maximum driving performance for the safety of the system and to limit the output torque accordingly. The maximum torque that can be obtained from the motor is calculated separately, based on instant sensor data and predetermined and/or instant system limits and the smallest of these is determined as the available torque.

The acceleration limit is an important factor affecting driving comfort and safety. In addition, the acceleration limiting feature according to the applications allows the vehicle to be used in different driving modes (for example, to increase energy efficiency). Limitation according to the start up condition prevents the motor driver components from being damaged or early aging as a result of the user applying high torque for a long time while the rotor is locked. The fact that the rotor does not move despite the maximum torque for a certain period of time indicates that there is a mechanical obstacle, and this obstacle must be removed. As long as the obstacle is not removed, applying the maximum torque for a longer time will lead to unnecessary losses and heating. These problems are eliminated with the aforementioned method.

The aim of the invention is to obtain a torque calculation method with limiting algorithms according to motor and motor driver temperature, battery current and voltage information, output power, motor line current, acceleration limit andstart up condition. Said method has hysteresis application and adaptive parameters.

The structural and characteristic features of the present invention will be understood clearly by the following drawings and the detailed description made with reference to these drawings. Therefore, the evaluation shall be made by taking these figures and the detailed description into consideration.

Description of the Figures

Figure 1 is an example block diagram view of the use of the invention.

Figure 2 is the detail view of the block diagram of the invention.

Figure 3 is the hysteresis algorithm of the invention.

Description of the Part References

1. Applicable torque calculation module

1.1. Available torque calculation module depending on drive temperature

1.2. Available torque calculation module depending on motor temperature

1.3. Available torque calculation module depending on battery current

1.4. Available torque calculation module depending on battery voltage

1.5. Available torque calculation module depending on motor output power

1.6. Available torque calculation module depending on the motor line current

1.7. Available torque calculation module depending on motor acceleration

1.8. Available torque calculation module depending on the start up condition

1.9. Comparison module

2. Torque limiter module

Tavaii.: Available torque value

Uparam: Instant value of the limiting parameter Bandwidth defined around the limit U param im: Limit value of the limiting parameter

Detailed Description of the Invention

In this detailed description, the preferred embodiments of the invention are described only for clarifying the subject matter in a manner such that no limiting effect is created.

In the inventive maximum torque calculation method that can be applied for the electric vehicle motors, the maximum torque that can be applied instantly is determined by the available torque calculation module (1 ) and the applied torque is limited when necessary by the torque limiting module (2). Thus, the functional safety of the system along with the maximum efficiency driving performance is achieved.

The available torque calculation module (1) calculates the maximum torque that can be obtained from the motor based on instant sensor data and predetermined and/or instant system limits. Said sensor data are motor and driver temperatures, battery current and voltage information, motor speed and motor phase current values. The calculated torque information is an input to the torque limiter module (2) along with the torque command. Thus, it is ensured that the applied torque value is not higher than the calculated limit value.

Available torque calculation module (1 ) comprises of the following; available torque calculation module (1.1 ) depending on the drive temperature, available torque calculation module (1.2) depending on motor temperature, available torque calculation module (1.3 depending on battery current, available torque calculation module (1.4) depending on battery voltage, available torque calculation module (1.5) depending on motor output power, available torque calculation module (1.6) depending on motor line current, available torque calculation module (1.7) depending on motor acceleration, available torque calculation module (1.8) depending on start up condition and comparison module (1.9). Torque is calculated separately for each parameter with the mentioned modules and the smallest of the calculation result is determined as the available torque limit.

The available torque calculation module depending on the driver temperature (1.1 ), , reads the temperature information of the motor driver and gradually reduces the applied torque depending on the magnitude of exceeding the temperature limit. The number of stages, range and torque derating percentages are parameters that can be changed according to the application. For example, the applied torque is reduced by 25% when exceeding the limit by 0.5°C, 50% when exceeding by 1°C, 75% when exceeding by 1.5°C, and 100% when exceeding by more than 1.5°C, therefore torque is reduced in four steps at 0.5°C intervals. When the temperature value falls below the limit values by as much as the hysteresis value, again the torque is given gradually in a similar way.

The available torque calculation module depending on the motor temperature (1.2), , reads the motor temperature information and gradually reduces the applied torque depending on the extent of exceeding the temperature limit. As with the drive temperature, the number of steps, range and torque derating percentages are parameters that can be changed according to the application. When the temperature value falls below the limit values by as much as the hysteresis value, the torque is given again gradually in a similar way.

The available torque calculation module depending on the battery current (1.3), with its two-stage calculation algorithm, limits the torque that can be applied so that the battery current does not exceed the battery discharge current limit in the traction state and the battery charge current limit in the regenerative braking situation. In the first stage, the approximate torque value that can be applied from the input-output power values is calculated by using the battery voltage, motor speed, battery current limits and system efficiency. Thus, even if the applied torque is lower than the limit values, the approximate regenerative and traction torque values can be reported to the user. In the second stage, when the battery current exceeds the limit, the applied torque is reduced in certain steps. Thus, the actual value corresponding to the current limits of the approximately calculated torque value in the first stage is determined. When the current value falls below the limit values by the hysteresis value, the torque is given again in certain steps.

The available torque calculation module depending on the battery voltage (1.4), , reads the battery voltage information and gradually limits the applied torque such that the voltage value does not fall below the minimum battery voltage limit in case of traction, and it does not exceed the maximum battery voltage limit in case of regenerative braking.. Similarly, a hysteresis structure is used to release the torque.

The available torque calculation module depending on the motor output power (1.5), , calculates the torque value that can be applied according to the mechanical output power limit by reading the motor speed information. After a certain speed, the torque that can be applied is linearly reduced to zero. The available torque calculation module depending on the motor line current (1.6), , provides torque limitation such that the resultant of the applied field weakening current and torque current does not exceed the maximum line current limit. Field weakening current is applied in permanent magnet synchronous motors to reach high speeds.

The available torque calculation module depending on the motor acceleration(1.7), , limits the applied torque to certain steps such that the motor speed increase rate does not exceed the acceleration limit. Similarly, a hysteresis structure is used to release the torque. The instant acceleration value is obtained by using the motor speed and oscillations are prevented by passing it through a low-pass filter.

The available torque calculation module depending on the start up condition (1.8), , ensures that the torque that can be applied in the start up state is applied without exceeding the determined time limit. In the start up state (at zero motor speed), the motor driver unit switching elements are thermally stressed. Starting torque must not be applied continuously so as to protect the switching components. Said module (1.8) operates an integral counter as soon as the applied torque is higher than the continuous torque that can be applied. When the counter value reaches the limit value, it gradually reduces the available torque to the continuous torque value. The limit value is obtained by multiplying the maximum starting torque by the specified time limit. Thus, lower torque values can be given with higher times. After a certain period of time, the applied torque is given again gradually.

The comparison module (1.9) takes the calculated torque values and compares the values it receives and determines the smallest torque value as the available torque limit.

While determining the available torque, trying to keep any limiting parameter constant at the limit value will cause the oscillations in the relevant parameter to be reflected directly to the available torque value, and thus to the output torque. As a solution to this problem, instead of trying to keep the parameter value (U _pa ram) at the limit value (U _pa ram, iim), a hysteresis structure was used to keep it in a defined band gap (+MJ _hyst ) around the limit. As seen in Figure 3, the available torque value (T _ava ii.) is not changed if the limiting parameter (U _par am) remains within this defined band. Thus, problems such as unstable driving, low comfort, and aging of electro-mechanical components, which may be caused by oscillations in the output torque, are prevented. Hysteresis, torque derating and restoring steps and limit values in all modules are parameters that can be changed according to the application. These parameters, which can be changed with the user interface, can be written to non-volatile memory. Thus, it is customized for different vehicle applications, operating conditions and driving modes.