CN116512933A - Output torque optimization method for electric light truck motor - Google Patents

Abstract

The invention discloses an electric light-truck motor output torque optimization method, which is used for building an integral framework of a control strategy from three parts of motor torque checking, rear axle bearing checking and torque command map. Aiming at motor torque output, a motor torque output interval is limited, motor torque output precision is optimized, motor torque is enabled to be in linear change in the output process, and on the basis of meeting various driving conditions, output torque of a motor is thinned, so that torque output is smoother. The invention not only can solve the driving requirements of various working conditions, but also can meet the driving intention requirements of drivers, and can also protect each high-voltage component to work under the allowable working conditions, thereby prolonging the service life of the high-voltage component. And the method can be implemented to the use of the electric light truck based on the current actual conditions, and further can collect and accumulate parameters for optimizing the torque output of the motor on the basis for optimizing and improving the power performance of the subsequent product.

Description

Output torque optimization method for electric light truck motor

Technical Field

The invention relates to the technical field of electric light cards, in particular to an output torque optimization method of an electric light card motor.

Background

The driving motors used by the electric light truck type in the current market are basically permanent magnet synchronous alternating current motors, and the control modes of the motors mainly comprise a torque control mode and a rotating speed control mode. The torque mode is that a Vehicle Control Unit (VCU) outputs a torque command to control the motor to output torque according to an opening signal of an accelerator pedal, and compared with the rotating speed mode, the torque mode takes driving intention of a driver into consideration more, and meets actual driving requirements more. The torque control mode is used more in the motor control mode.

The control command for the motor output torque is a torque command output by a Vehicle Control Unit (VCU) in combination with an accelerator opening signal and a motor torque characteristic curve. At present, algorithms for calculating motor torque instructions of a light truck electric vehicle on a whole vehicle controller in the market are various, but consideration of whole vehicle information is lacking. The dynamic performance of the vehicle cannot meet the driving requirements of various working conditions.

Specifically, the power system of the existing electric light truck direct-drive motor mainly comprises a whole Vehicle Controller (VCU), an accelerator pedal, a Motor Controller (MCU), a high-voltage distribution box (PDU), a drive motor, a frame, a transmission shaft, a rear axle and tires. The whole vehicle controller outputs a torque command by collecting an accelerator pedal opening signal, and a Motor Controller (MCU) responds to the torque command of the whole vehicle controller by controlling a driving motor. Wherein, the upper and lower limit values of the motor torque are determined by the external characteristics of the motor. The existing torque control strategy only refines the motor torque output from the accelerator opening signal and the motor external characteristic curve, and the influence of other components on the motor torque value output is not considered by the system. Factors such as the load of the whole vehicle, the full load climbing capacity, the bearing capacity of a rear axle, the output power of a battery, the speed of the vehicle and the like can have key influence on a torque command output by a whole Vehicle Controller (VCU). The lack of key parameter checking not only can lead to motor torque output not to fully meet various running conditions and driving requirements, but also can produce certain adverse effects on various components, such as reducing the service lives of components such as a rear axle, a battery and a motor.

Disclosure of Invention

In view of the foregoing, the present invention is directed to providing a method for optimizing output torque of an electric light-truck motor, so as to solve the aforementioned technical problems.

The technical scheme adopted by the invention is as follows:

the invention provides a motor output torque optimization method for an electric light truck, which comprises the following steps:

checking the climbing performance of the motor torque under the full-load working condition of the electric light truck;

checking whether the maximum torque of the motor is overloaded or not through the bearing capacity of the rear axle;

after the two checks are completed, a torque command map related to the change of the vehicle speed is constructed;

and in the actual control stage, acquiring the real-time accelerator opening and the current vehicle speed, and determining the current motor output torque control instruction by inquiring the torque instruction mapping chart.

In at least one possible implementation, the motor output torque is limited by a coasting resistance and a ramp resistance.

In at least one possible implementation thereof, the limiting the motor output torque by the coasting resistance and the ramp resistance includes:

calculating the sliding resistance when the vehicle is fully loaded;

calculating the climbing resistance of a vehicle passing through a preset gradient ramp when the vehicle is fully loaded;

and checking the motor torque based on the sliding resistance and the climbing resistance.

In at least one possible implementation manner, the checking whether the maximum torque of the motor is overloaded via the bearing capacity of the rear axle includes:

calculating the maximum torque value exerted on the rear axle by the motor according to the external characteristics of the motor;

calculating the ratio between the maximum allowable torque value of the rear axle and the actual maximum torque value of the motor;

and judging whether the maximum torque value of the motor exceeds the bearing capacity of the rear axle based on the comparison relation between the ratio and a preset rear axle safety coefficient.

In at least one possible implementation manner, the determining whether the maximum torque value of the motor exceeds the rear axle bearing capacity includes:

if the ratio is greater than or equal to the rear axle safety coefficient, the maximum output torque of the motor is represented to be not exceeding the bearing capacity of the rear axle;

and if the ratio is smaller than the rear axle safety coefficient, the maximum torque value of the motor is represented to exceed the bearing capacity of the rear axle, and the maximum torque output value of the motor is limited within the rear axle safety coefficient.

In at least one possible implementation manner, the constructing a torque command map related to vehicle speed variation includes:

calculating the speed of the vehicle according to the rotating speed of the motor;

according to preset peak power, peak torque, peak rotating speed, tire radius, rear axle speed ratio and vehicle speed of the motor, preliminarily obtaining the relation of actual output torque values of the motor at different speeds;

based on the relation, the maximum torque value which can be output by the motor torque along with the change of the vehicle speed is obtained, and the torque command mapping chart is formed by combining the accelerator opening and the vehicle speed signal.

Compared with the prior art, the main design concept of the invention is to build an integral framework of a control strategy from three parts of motor torque check, rear axle bearing check and torque command map. Aiming at motor torque output, a motor torque output interval is limited, motor torque output precision is optimized, motor torque is enabled to be in linear change in the output process, and on the basis of meeting various driving conditions, output torque of a motor is thinned, so that torque output is smoother. Specifically, the motor output torque is limited through the sliding resistance and the ramp resistance, whether the maximum torque of the motor is overloaded or not is checked through the bearing capacity of the rear axle, the maximum speed of the motor at each speed point is limited through the speed, and finally the final output torque of the motor is refined through the opening degree of an accelerator and the speed. The invention not only can solve the driving requirements of various working conditions, but also can meet the driving intention requirements of drivers, and can also protect each high-voltage component to work under the allowable working conditions, thereby prolonging the service life of the high-voltage component. And the method can be implemented to the use of the electric light truck based on the current actual conditions, and further can collect and accumulate parameters for optimizing the torque output of the motor on the basis for optimizing and improving the power performance of the subsequent product.

Drawings

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described with reference to the accompanying drawings, in which:

fig. 1 is a schematic flow chart of an output torque optimizing method of an electric light-truck motor according to an embodiment of the present invention.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.

The invention provides an embodiment of an electric light-truck motor output torque optimization method, specifically as shown in fig. 1, which comprises the following steps:

s1, checking climbing performance of motor torque under the full-load working condition of an electric light truck;

the purpose of motor torque verification is to verify that the maximum torque of the motor can meet the climbing performance of the vehicle passing through a preset gradient (such as a 30% gradient) under the full load condition.

Specifically, the core idea of implementing this step is to limit the motor output torque through the coasting resistance and the ramp resistance, and in actual operation, the following steps may be included:

(1) Calculating the sliding resistance when the vehicle is fully loaded:

T _{row of lines} The running resistance N.m when the vehicle is fully loaded; f0, F1 and F2 are respectively the sliding resistance coefficient N/(km/h); r is the rolling radius m of the tire; v is the current speed km/h of the vehicle; i _{Main unit} Is the main speed reduction ratio of the vehicle.

(2) Calculating the climbing resistance through a preset gradient ramp when the vehicle is fully loaded:

T _{slope with a slope surface} The resistance N.m of the ramp for climbing the slope when the vehicle is fully loaded; m is the total mass kg of the vehicle when the vehicle is fully loaded; θ is a ramp grade value; i _{Main unit} Is the main speed reduction ratio of the vehicle; r is the tire rolling radius m.

(3) Checking motor torque based on the sliding resistance and the climbing resistance:

T _{management device} ＝(T _{Row of lines} ×T _{Slope with a slope surface} )×1.3

T _{Electric power} ≥T _{Management device}

T _{Management device} Calculating the maximum motor output torque N.m required by the vehicle passing through the ramp for theory; 1.3 is an experience coefficient; t (T) _{Electric power} The maximum torque N.m can be output for the motor.

From the above, it is necessary to calculate the sliding resistance T of the vehicle during sliding according to the sliding resistance coefficient and the whole vehicle information when the vehicle is in the full load state _{Row of lines} Then, the slope resistance T of the vehicle when passing through the slope is calculated according to the slope information _{Slope with a slope surface} Considering that the environment and other factors of the vehicle can also influence the passing performance of the whole vehicle, setting an empirical coefficient according to experimental accumulation, and finally obtaining the upper limit value of the motor torque to meet the requirement of the calculation formula.

S2, checking whether the maximum torque of the motor is overloaded or not through the bearing capacity of the rear axle;

specifically, first, the maximum torque value applied to the rear axle by the motor is calculated from the external characteristics of the motor:

tsut = tset x I master x 0.95

T _{Electric power} The maximum torque N.m can be output for the motor actually; t (T) _{Conveying device} Maximum torque value N.m applied to the rear axle for the motor; 0.95 is the transmission coefficient from the motor to the rear axle; i _{Main unit} Is the main speed reduction ratio of the vehicle;

secondly, calculating the ratio between the maximum allowable torque value of the rear axle and the actual maximum torque value of the motor:

T _{rear part (S)} Is a rear axleMaximum torque value n·m allowed to be output; t (T) _{Conveying device} Maximum torque value N.m applied to the rear axle for the motor;

and then, based on the comparison relation between the ratio and the preset rear axle safety coefficient, judging whether the maximum torque value of the motor exceeds the bearing capacity of the rear axle. Specifically:

if t is more than or equal to 1.5 (the safety coefficient of the rear axle), the maximum output torque of the motor is not more than the bearing capacity of the rear axle, and the torque output of the motor can reach the maximum value;

if t < 1.5 (rear axle safety factor), it means that the maximum torque value of the motor exceeds the bearing capacity of the rear axle, for which the maximum torque output of the motor needs to be limited within the rear axle safety factor.

Step S3, constructing a torque command map related to vehicle speed change:

in actual operation, it may specifically include:

s31, calculating the vehicle speed according to the motor rotation speed:

v is the speed km/h; n is the motor rotation speed rpm; r is the rolling radius m of the tire; i _{Main unit} Is the main speed reduction ratio of the vehicle.

S32, preliminarily obtaining the relation of actual output torque values of the motor at different rotating speeds according to the peak power, peak torque, peak rotating speed, tire radius, rear axle speed ratio and vehicle speed of the motor;

the formula on which this link is based is referenced below:

p is motor power kw; n is the motor rotation speed rpm; t is motor torque N.m.

For example: peak power P of certain motor _{Peak to peak} =160 kw, peak rotation speed n _{Peak to peak} Peak torque t=4800 rpm _{Peak to peak} Tire radius r=0.36 m, rear axle speed ratio I _{Main unit} =5, the torque values of the motor at different rotational speeds can be calculated preliminarily, as shown in the following table:

vehicle speed (km/h)	0	8.1	16.3	24.4	32.6	40.7	48.9	57.0	65 .1	73 .3	81 .4	89 .6	97 .7	10 5. 9	11 4. 0	12 2. 1	130.3
																		Motor rotation speed (rpm)	0	300	600	900	1200	1500	1800	2100	24 00	27 00	30 00	33 00	36 00	39 00	42 00	45 00	4800
Peak power (kw)	160	160	160	160	160	160	160	160	16 0	16 0	16 0	16 0	16 0	16 0	16 0	16 0	160
																		Peak torque (N · m)	1200	1200	1200	1200	1200	1200	1200	1200	12 00	12 00	12 00	12 00	12 00	12 00	12 00	12 00	1200
Calculate torque (N · m)	/	5093. 333	2546.7	1697.8	1273.3	1018. 7	848.9	727.6	63 6. 7	56 5. 9	50 9. 3	46 3. 0	42 4. 4	39 1. 8	36 3. 8	33 9. 6	318.3
																		Adjusting the excess torque Point (N.m)	1200	1200	1200	1200	1200	1018. 667	848.8 889	727.6 19	63 6. 7	56 5. 9	50 9. 3	46 3	42 4. 4	39 1. 8	36 3. 8	33 9. 6	318.3

As can be seen from the above table, the motor torques corresponding to different vehicle speed points are different, and in the low vehicle speed section, the calculated motor torque exceeds the peak motor torque, so that the motor torque of the part can be adjusted to be the peak motor torque; when the vehicle speed increases, the maximum torque that the motor can output gradually decreases, and the portion below the peak torque may take the actual output torque value of the motor as the maximum torque value.

And S33, obtaining a maximum torque value which can be output when the motor torque changes along with the speed of the vehicle based on the relation, and constructing the torque command map by combining the opening degree of the accelerator and the speed signal of the vehicle.

The maximum torque value which can be output when the motor torque changes along with the speed of the vehicle is calculated by the table, and under the consideration of the factors of the accelerator opening and the speed signal, a complete torque command map can be calculated, as shown in the following table:

the maximum torque output by the motor limited by different vehicle speed points can be determined through the map, the torque value corresponding to each vehicle speed point is thinned by different accelerator opening degrees, and the torque output of the motor is thinned through double restriction of the accelerator opening degrees and the vehicle speed signals, so that the torque output of the motor is smoother.

And step S4, acquiring real-time accelerator opening and current vehicle speed in an actual control stage, and determining a current motor output torque control instruction by inquiring the torque instruction map.

That is, in the actual motor torque control process of the electric light truck, only the current vehicle speed and the accelerator opening are required to be obtained, and then the map is queried to directly configure the corresponding motor torque control instruction.

In summary, the main design concept of the invention is to build an overall framework of control strategy from three parts of motor torque check, rear axle load check and torque command map. Aiming at motor torque output, a motor torque output interval is limited, motor torque output precision is optimized, motor torque is enabled to be in linear change in the output process, and on the basis of meeting various driving conditions, output torque of a motor is thinned, so that torque output is smoother. The motor output torque can be limited by the sliding resistance and the ramp resistance, whether the maximum torque of the motor is overloaded or not is checked through the bearing capacity of the rear axle, the maximum speed of the motor at each speed point is limited through the speed, and finally the final output torque of the motor is refined through the opening degree of an accelerator and the speed. The invention not only can solve the driving requirements of various working conditions, but also can meet the driving intention requirements of drivers, and can also protect each high-voltage component to work under the allowable working conditions, thereby prolonging the service life of the high-voltage component. And the method can be implemented to the use of the electric light truck based on the current actual conditions, and further can collect and accumulate parameters for optimizing the torque output of the motor on the basis for optimizing and improving the power performance of the subsequent product.

In the embodiments of the present invention, "at least one" means one or more, and "a plurality" means two or more. "and/or", describes an association relation of association objects, and indicates that there may be three kinds of relations, for example, a and/or B, and may indicate that a alone exists, a and B together, and B alone exists. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. "at least one of the following" and the like means any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c may represent: a, b, c, a and b, a and c, b and c or a and b and c, wherein a, b and c can be single or multiple.

The construction, features and effects of the present invention are described in detail according to the embodiments shown in the drawings, but the above is only a preferred embodiment of the present invention, and it should be understood that the technical features of the above embodiment and the preferred mode thereof can be reasonably combined and matched into various equivalent schemes by those skilled in the art without departing from or changing the design concept and technical effects of the present invention; therefore, the invention is not limited to the embodiments shown in the drawings, but is intended to be within the scope of the invention as long as changes made in the concept of the invention or modifications to the equivalent embodiments do not depart from the spirit of the invention as covered by the specification and drawings.

Claims (6)

1. An electric light truck motor output torque optimization method is characterized by comprising the following steps:

checking the climbing performance of the motor torque under the full-load working condition of the electric light truck;

checking whether the maximum torque of the motor is overloaded or not through the bearing capacity of the rear axle;

after the two checks are completed, a torque command map related to the change of the vehicle speed is constructed;

and in the actual control stage, acquiring the real-time accelerator opening and the current vehicle speed, and determining the current motor output torque control instruction by inquiring the torque instruction mapping chart.

2. The method of optimizing motor output torque for an electric light truck of claim 1 wherein motor output torque is limited by coasting resistance and ramp resistance.

3. The method of optimizing motor output torque for an electric light truck of claim 2 wherein limiting motor output torque through coasting resistance and ramp resistance comprises:

calculating the sliding resistance when the vehicle is fully loaded;

calculating the climbing resistance of a vehicle passing through a preset gradient ramp when the vehicle is fully loaded;

and checking the motor torque based on the sliding resistance and the climbing resistance.

4. The method of claim 1, wherein checking whether the motor maximum torque is overloaded via the rear axle load capacity comprises:

calculating the maximum torque value exerted on the rear axle by the motor according to the external characteristics of the motor;

calculating the ratio between the maximum allowable torque value of the rear axle and the actual maximum torque value of the motor;

and judging whether the maximum torque value of the motor exceeds the bearing capacity of the rear axle based on the comparison relation between the ratio and a preset rear axle safety coefficient.

5. The method of claim 4, wherein determining whether the motor torque capacity exceeds the rear axle capacity comprises:

if the ratio is greater than or equal to the rear axle safety coefficient, the maximum output torque of the motor is represented to be not exceeding the bearing capacity of the rear axle;

and if the ratio is smaller than the rear axle safety coefficient, the maximum torque value of the motor is represented to exceed the bearing capacity of the rear axle, and the maximum torque output value of the motor is limited within the rear axle safety coefficient.

6. The method of optimizing output torque of an electric light truck motor according to any one of claims 1 to 5, wherein the constructing a torque command map related to a change in vehicle speed includes:

calculating the speed of the vehicle according to the rotating speed of the motor;

according to preset peak power, peak torque, peak rotating speed, tire radius, rear axle speed ratio and vehicle speed of the motor, preliminarily obtaining the relation of actual output torque values of the motor at different speeds;

based on the relation, the maximum torque value which can be output by the motor torque along with the change of the vehicle speed is obtained, and the torque command mapping chart is formed by combining the accelerator opening and the vehicle speed signal.