Unmanned forklift stacking method and system based on synchronous motor field weakening control

Abstract

An unmanned forklift stacking method based on synchronous motor field weakening control is characterized by comprising the steps of goods obtaining and goods stacking. The cargo obtaining step comprises the following steps: obtaining the difference between the height of the cargo and the current height of a fork arm as a first difference value; judging whether the first difference value is greater than a height threshold value, if so, generating a first current signal of the synchronous motor, and if not, generating a second current signal of the synchronous motor; the first current signal or the second current signal is input into a controller, so that the height of the fork arm is adjusted to the height of goods; different operation parameters are obtained through different sensors, automatic and intelligent control over the synchronous motor is achieved when cargoes are stacked, the labor cost is reduced, and the production efficiency and the cargo transportation stability during stacking are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned forklifts, and in particular to an unmanned forklift stacking method and system based on weak magnetic control of a synchronous motor. Background Art

[0002] With the advancement of science and technology and the improvement of technological innovation, many companies have adopted automated assembly lines in production to achieve large-scale batch production. Due to the increase in production volume, current companies need to stack the products after production in the warehouse to facilitate subsequent product delivery.

[0003] At present, when palletizing, the motor current input of the unmanned forklift is manually adjusted to achieve the lifting of the fork arm. However, due to the limited manual operation, the lifting switch is adjusted based on human experience for goods at different heights and weights. At this time, the current input may be too large, causing the fork arm to shake, thus affecting the stability of palletizing. Summary of the invention

[0004] In view of the above-mentioned defects, the object of the present invention is to provide an unmanned forklift stacking method and system based on weak magnetic control of synchronous motor.

[0005] To achieve this purpose, the present invention adopts the following technical solutions: an unmanned forklift stacking method based on weak magnetic control of synchronous motor, including obtaining goods and stacking goods;

[0006] The steps to obtain the goods are as follows:

[0007] Obtain the difference between the height of the cargo and the current height of the fork arm as the first difference;

[0008] Determine whether the first difference is greater than a height threshold, if so, generate a first current signal of the synchronous motor, if less than the height threshold, generate a second current signal of the synchronous motor;

[0009] Inputting the first current signal or the second current signal into the controller so that the height of the fork arm is adjusted to the height of the cargo;

[0010] The steps for stacking goods are as follows:

[0011] The weight of the goods is obtained, and then it is determined whether the weight of the goods is less than the weight threshold. If it is less than the weight threshold, the difference between the current height of the fork arm and the stacking height is obtained as the second difference;

[0012] Determine whether the second difference is greater than a height threshold, and if so, generate a first current signal of the synchronous motor; if less than the height threshold, generate a second current signal of the synchronous motor;

[0013] If it is greater than the weight threshold, a third current signal of the synchronous motor is generated according to the weight of the cargo;

[0014] The first current signal, the second current signal or the third current signal is input into the controller so that the height of the fork arm is adjusted to the height of the stacking position.

[0015] Preferably, the first current signal includes a first sub-signal and a second sub-signal;

[0016] Controlling the current of the synchronous motor under the control of the first sub-signal so that the speed of the synchronous motor is increased to a first speed;

[0017] When the first speed is reached, the current of the synchronous motor is controlled by the second sub-signal.

[0018] Preferably, the step of obtaining the current in the first sub-signal is as follows: giving the synchronous motor a fixed torque, and obtaining the q-axis current I under the fixed torque by the MTPA method. q and the d-axis current I d ;

[0019] The steps for obtaining the current in the second sub-signal are as follows:

[0020] Get the given current I of the q axis in real time qRef , the given current I qRef Input to the low-pass filter to get the first parameter I' qRef ;

[0021] Get the feedback current I of the q axis in real time q , the given current I q Input to the low-pass filter to obtain the second parameter I' q ;

[0022] Get the first parameter I' qRef and the second parameter I′ q The difference E is used as the input of the PI controller to obtain the current feedback given term D1;

[0023] According to the rated current I n and rated speed ω n Calculate the amplification factor Kc of the feedforward given term of the weak magnetic current;

[0024] The speed increment of the current weak magnetic field is obtained, and the speed increment is adjusted by the amplification factor Kc to obtain the current feedback given item D2;

[0025] The d-axis current I is obtained by adding the feedback given term D1 and the feedforward given term D2. d ;

[0026] According to the maximum current and the current of the d-axis, the maximum limit value I of the q-axis current is obtained. Q .

[0027] Preferably, the second current signal acquisition method is: giving the synchronous motor a fixed torque, and obtaining the q-axis current I under the fixed torque by the MTPA method. q and the d-axis current I d .

[0028] Preferably, the steps of generating the third current signal are as follows:

[0029] Obtain the friction coefficient of the pallet where the goods are located, and obtain the friction force of the pallet on the forklift based on the friction coefficient;

[0030] Obtaining the torque required by the synchronous motor according to the friction force, the weight of the cargo and the pallet, and the second difference;

[0031] The required torque is input into the current output model to obtain the required d-axis current and q-axis current of the synchronous motor;

[0032] The formula for obtaining the required torque is as follows:

[0033]

[0034] Where W is the weight of the pallet and the goods, g is the acceleration of gravity, F is the friction force, λ is the adjustment coefficient, and r is the conversion factor;

[0035] The current output model is as follows:

[0036]

[0037] Where γ is a constant factor greater than 0, p is the number of pole pairs of the synchronous motor, n is the number of turns of each phase winding, ψ is the flux generated by the permanent magnet, and Ld and Lq are the inductances on the d-axis and q-axis of the synchronous motor respectively.

[0038] An unmanned forklift stacking system based on weak magnetic field control of a synchronous motor, using the unmanned forklift stacking method based on weak magnetic field control of a synchronous motor, comprising a cargo acquisition module and a cargo stacking module;

[0039] The cargo acquisition module is used to acquire the difference between the height of the cargo and the current height of the fork arm as the first difference;

[0040] Determine whether the first difference is greater than a height threshold, if so, generate a first current signal of the synchronous motor, if less than the height threshold, generate a second current signal of the synchronous motor;

[0041] Inputting the first current signal or the second current signal into the controller so that the height of the fork arm is adjusted to the height of the cargo;

[0042] The cargo stacking module is used to obtain the weight of the cargo, and then determine whether the cargo weight is less than the weight threshold. If it is less than the weight threshold, the difference between the current height of the fork arm and the stacking height is obtained as the second difference;

[0043] Determine whether the second difference is greater than a height threshold, and if so, generate a first current signal of the synchronous motor; if less than the height threshold, generate a second current signal of the synchronous motor;

[0044] If it is greater than the weight threshold, a third current signal of the synchronous motor is generated;

[0045] The first current signal, the second current signal or the third current signal is input into the controller so that the height of the fork arm is adjusted to the height of the stacking position.

[0046] Preferably, the cargo acquisition module includes a first current signal module;

[0047] The first current signal module is used to control the current of the synchronous motor under the control of the first sub-signal, so that the speed of the synchronous motor is increased to a first speed;

[0048] When the first speed is reached, the current of the synchronous motor is controlled by the second sub-signal.

[0049] Preferably, the first current signal module includes a first sub-signal acquisition unit and a second sub-signal acquisition unit;

[0050] The first sub-signal acquisition unit is used to give the synchronous motor a fixed torque, and obtain the q-axis current I under the fixed torque through the MTPA method. q and the d-axis current I d ;

[0051] The second sub-signal acquisition unit is used to acquire the given current I of the q-axis in real time. qRef , the given current I qRef Input to the low-pass filter to get the first parameter I' qRef ;

[0052] Get the feedback current I of the q axis in real time q , the given current I q Input to the low-pass filter to obtain the second parameter I' q ;

[0053] Get the first parameter I' qRef and the second parameter I′ q The difference E is used as the input of the PI controller to obtain the current feedback given term D1;

[0054] According to the rated current In and rated speed ω n Calculate the amplification factor Kc of the feedforward given term of the weak magnetic current;

[0055] The speed increment of the current weak magnetic field is obtained, and the speed increment is adjusted by the amplification factor Kc to obtain the current feedback given item D2;

[0056] The d-axis current I is obtained by adding the feedback given term D1 and the feedforward given term D2. d ;

[0057] According to the maximum current and the current of the d-axis, the maximum limit value I of the q-axis current is obtained. Q .

[0058] Preferably, the cargo stacking module includes a third signal generating unit, and the third signal generating unit is used to obtain the friction coefficient of the pallet where the cargo is located, and obtain the friction force of the pallet on the forklift according to the friction coefficient;

[0059] Obtaining the torque required by the synchronous motor according to the friction force, the weight of the cargo and the pallet, and the second difference;

[0060] The required torque is input into the current output model to obtain the required d-axis current and q-axis current of the synchronous motor.

[0061] One of the above technical solutions has the following advantages or beneficial effects: In the present invention, different operating parameters are obtained through different sensors to realize automatic and intelligent control of the synchronous motor when the goods are palletized, which helps to reduce labor costs, improve production efficiency and the stability of cargo transportation during palletizing. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a flow chart of goods acquisition in one embodiment of the method of the present invention.

[0063] Figure 2 It is a flow chart of goods stacking in one embodiment of the method of the present invention.

[0064] Figure 3 It is a schematic diagram of the structure of an embodiment of the system of the present invention. DETAILED DESCRIPTION

[0065] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0066] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0067] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0068] like Figures 1 to 3 As shown, an unmanned forklift stacking method based on weak magnetic control of a synchronous motor includes obtaining goods and stacking goods;

[0069] The steps to obtain the goods are as follows:

[0070] Obtain the difference between the height of the cargo and the current height of the fork arm as the first difference;

[0071] Determine whether the first difference is greater than a height threshold, if so, generate a first current signal of the synchronous motor, if less than the height threshold, generate a second current signal of the synchronous motor;

[0072] Inputting the first current signal or the second current signal into the controller so that the height of the fork arm is adjusted to the height of the cargo;

[0073] The steps for stacking goods are as follows:

[0074] The weight of the goods is obtained, and then it is determined whether the weight of the goods is less than the weight threshold. If it is less than the weight threshold, the difference between the current height of the fork arm and the stacking height is obtained as the second difference;

[0075] Determine whether the second difference is greater than a height threshold, and if so, generate a first current signal of the synchronous motor; if less than the height threshold, generate a second current signal of the synchronous motor;

[0076] If it is greater than the weight threshold, a third current signal of the synchronous motor is generated according to the weight of the cargo;

[0077] The first current signal, the second current signal or the third current signal is input into the controller so that the height of the fork arm is adjusted to the height of the stacking position.

[0078] In the present invention, the power component of the unmanned forklift for driving the fork arm is a synchronous motor, and the control of the synchronous motor is mainly achieved by controlling the d-axis current and the q-axis current in the motor to control the lifting speed.

[0079] When acquiring goods, the fork arm is raised or lowered to the corresponding height. At this time, since there is no goods in the fork arm, there is no need to consider the influence of the weight of the goods on the output of the synchronous motor. At this time, only the up and down lifting distance needs to be considered. Therefore, when the lifting distance reaches a certain length, the speed of the synchronous motor will reach the turning speed, so that the synchronous motor enters the stage of weak magnetic control. Therefore, when acquiring goods, different first current signals or second current signals will be generated according to different first differences to ensure the smooth lifting of the fork arm.

[0080] When stacking goods, since there are goods on the fork arm, it is necessary to consider the effect of the weight of the goods on the fork arm. For this purpose, it is necessary to determine whether the weight of the goods is less than the weight threshold. If it is less than the weight threshold, the effect of the weight of the goods on the motor can be ignored. At this time, different currents are still generated through the second difference. When the weight of the goods is greater than the weight threshold, it is necessary to generate a third current signal of the synchronous motor according to the weight of the goods. The present invention takes into account the effect of the weight of the goods on the current input in the synchronous motor, thereby improving the stability of the forklift when stacking goods.

[0081] In the present invention, different operating parameters are obtained through different sensors to realize automatic and intelligent control of the synchronous motor when the goods are palletized, which helps to reduce labor costs, improve production efficiency and the stability of cargo transportation during palletizing.

[0082] Preferably, the first current signal includes a first sub-signal and a second sub-signal;

[0083] Controlling the current of the synchronous motor under the control of the first sub-signal so that the speed of the synchronous motor is increased to a first speed;

[0084] When the first speed is reached, the current of the synchronous motor is controlled by the second sub-signal.

[0085] Because when the first difference is greater than the height difference, the height distance adjusted by the fork arm of the unmanned forklift is longer, after the traditional MTPA method is used to adjust the current, the speed of the synchronous motor will reach the first speed (turning speed). At this time, the synchronous motor enters the weak magnetic control stage. At this time, it is necessary to generate the d-axis current and q-axis current in the weak magnetic control through the second sub-signal, so as to achieve stable lifting and lowering of the fork arm.

[0086] Preferably, the step of obtaining the current in the first sub-signal is as follows: giving the synchronous motor a fixed torque, and obtaining the q-axis current I under the fixed torque by the MTPA method. q and the d-axis current I d ;

[0087] The steps for obtaining the current in the second sub-signal are as follows:

[0088] Get the given current I of the q axis in real time qRef , the given current I qRef Input to the low-pass filter to get the first parameter I' qRef ;

[0089] Get the feedback current I of the q axis in real time q , the given current I q Input to the low-pass filter to obtain the second parameter I' q ;

[0090] By acquiring the given current and feedback current of the q-axis in real time and applying a low-pass filter for processing, more stable and accurate current parameters can be obtained. This method helps to accurately control the operation of the synchronous motor and improve stability and reliability.

[0091] Get the first parameter I' qRef and the second parameter I′ q The difference E is used as the input of the PI controller to obtain the current feedback given term D1;

[0092] By calculating the difference E between the given current and the feedback current and using it as the input of the PI controller, a feedback given term D1 for adjusting the current can be obtained. The PI controller can effectively reduce the error and improve the accuracy of current control.

[0093] The formula for obtaining the current feedback given term D1 is as follows:

[0094] D1(t)=K p E(t)+K i ∫E(t)dt;

[0095] Where t is time, K p With K i They are the proportional gain coefficient and the integral gain coefficient in the PI controller respectively;

[0096] According to the rated current I n and rated speed ω nThe amplification factor Kc of the feedforward given item of the weak magnetic current is calculated; the calculated amplification factor Kc is determined based on the rated current and rated speed of the motor, and the speed increment is adjusted by the amplification factor Kc, which can ensure that the motor runs in an efficient and stable state.

[0097] The formula for obtaining the amplification factor Kc is as follows:

[0098]

[0099] Among them I n is the rated current, ω n is the rated speed;

[0100] The speed increment of the current weak magnetic field is obtained, and the speed increment is adjusted by the amplification factor Kc to obtain the current feedback given item D2;

[0101] The formula for obtaining the feedforward given item D2 is as follows:

[0102] D2=-|(S t -S z )×Kc|; where S t is the target speed, S z is the turning speed.

[0103] The d-axis current I is obtained by adding the feedback given term D1 and the feedforward given term D2. d ;

[0104] According to the maximum current and the current of the d-axis, the maximum limit value I of the q-axis current is obtained. Q .

[0105]

[0106] Among them I max is the maximum output current, I d is the current of d axis.

[0107] At this time, when adjusting the q-axis current, the maximum limit value I Q As the current of the q-axis, it can increase the speed of the synchronous motor while ensuring stable operation, speeding up the fork arm to quickly reach the height where the cargo is.

[0108] Preferably, the second current signal acquisition method is: giving the synchronous motor a fixed torque, and obtaining the q-axis current I under the fixed torque by the MTPA method. q and the d-axis current I d .

[0109] Since the fixed torque given to the synchronous motor is fixed, the displacement distance (height threshold) of the fork arm when the speed of the synchronous motor reaches the first speed is fixed. Therefore, when the second current signal is determining the current, the synchronous motor has not entered the weak magnetic control stage. Therefore, the method of obtaining the second current signal is consistent with the method of obtaining the current in the first sub-signal.

[0110] Preferably, the steps of generating the third current signal are as follows:

[0111] Obtain the friction coefficient of the pallet where the goods are located, and obtain the friction force of the pallet on the forklift based on the friction coefficient;

[0112] When the weight of the goods is greater than the weight threshold, the synchronous motor needs to output a certain torque to achieve the lifting of the fork arm. For this reason, the friction coefficient of the pallet where the goods are located can be accurately calculated in the present invention, so that the friction of the pallet on the forklift can be accurately predicted, which helps the forklift to move the pallet and the goods on the pallet more smoothly during transportation or lifting. Avoid excessive torque, which may cause the pallet to slide or shake on the fork arm due to insufficient friction, thereby ensuring transportation stability and cargo safety.

[0113] Obtaining the torque required by the synchronous motor according to the friction force, the weight of the cargo and the pallet, and the second difference;

[0114] The required torque is input into the current output model to obtain the required d-axis current and q-axis current of the synchronous motor;

[0115] The formula for obtaining the required torque is as follows:

[0116]

[0117] Where W is the weight of the pallet and the goods, g is the acceleration of gravity, F is the friction force, λ is the adjustment coefficient, and r is the conversion factor;

[0118] The current output model is as follows:

[0119]

[0120] Where γ is a constant factor greater than 0, p is the number of pole pairs of the synchronous motor, n is the number of turns of each phase winding, ψ is the flux generated by the permanent magnet, and Ld and Lq are the inductances on the d-axis and q-axis of the synchronous motor respectively.

[0121] When the required torque of the motor is known, it can be input into the current output model, where the current output model limits the sum of the q-axis current and the d-axis current to a minimum value. While ensuring the ability to stably lift the fork arm, it can maximize energy efficiency and reduce unnecessary power loss, meeting the requirements of green and energy-saving modern production.

[0122] An unmanned forklift stacking system based on weak magnetic field control of a synchronous motor, using the unmanned forklift stacking method based on weak magnetic field control of a synchronous motor, comprising a cargo acquisition module and a cargo stacking module;

[0123] The cargo acquisition module is used to acquire the difference between the height of the cargo and the current height of the fork arm as the first difference;

[0124] Determine whether the first difference is greater than a height threshold, if so, generate a first current signal of the synchronous motor, if less than the height threshold, generate a second current signal of the synchronous motor;

[0125] Inputting the first current signal or the second current signal into the controller so that the height of the fork arm is adjusted to the height of the cargo;

[0126] The cargo stacking module is used to obtain the weight of the cargo, and then determine whether the cargo weight is less than the weight threshold. If it is less than the weight threshold, the difference between the current height of the fork arm and the stacking height is obtained as the second difference;

[0127] Determine whether the second difference is greater than a height threshold, and if so, generate a first current signal of the synchronous motor; if less than the height threshold, generate a second current signal of the synchronous motor;

[0128] If it is greater than the weight threshold, a third current signal of the synchronous motor is generated;

[0129] The first current signal, the second current signal or the third current signal is input into the controller so that the height of the fork arm is adjusted to the height of the stacking position.

[0130] Preferably, the cargo acquisition module includes a first current signal module;

[0131] The first current signal module is used to control the current of the synchronous motor under the control of the first sub-signal, so that the speed of the synchronous motor is increased to a first speed;

[0132] When the first speed is reached, the current of the synchronous motor is controlled by the second sub-signal.

[0133] Preferably, the first current signal module includes a first sub-signal acquisition unit and a second sub-signal acquisition unit;

[0134] The first sub-signal acquisition unit is used to give the synchronous motor a fixed torque, and obtain the q-axis current I under the fixed torque through the MTPA method. q and the d-axis current I d ;

[0135] The second sub-signal acquisition unit is used to acquire the given current I of the q-axis in real time. qRef , the given current I qRef Input to the low-pass filter to get the first parameter I' qRef ;

[0136] Get the feedback current I of the q axis in real time q , the given current I q Input to the low-pass filter to obtain the second parameter I q ′;

[0137] Get the first parameter I' qRef and the second parameter I′ q The difference E is used as the input of the PI controller to obtain the current feedback given term D1;

[0138] According to the rated current I n and rated speed ω n Calculate the amplification factor Kc of the feedforward given term of the weak magnetic current;

[0139] The speed increment of the current weak magnetic field is obtained, and the speed increment is adjusted by the amplification factor Kc to obtain the current feedback given item D2;

[0140] The d-axis current I is obtained by adding the feedback given term D1 and the feedforward given term D2. d ;

[0141] According to the maximum current and the current of the d-axis, the maximum limit value I of the q-axis current is obtained. Q .

[0142] Preferably, the cargo stacking module includes a third signal generating unit, and the third signal generating unit is used to obtain the friction coefficient of the pallet where the cargo is located, and obtain the friction force of the pallet on the forklift according to the friction coefficient;

[0143] Obtaining the torque required by the synchronous motor according to the friction force, the weight of the cargo and the pallet, and the second difference;

[0144] The required torque is input into the current output model to obtain the required d-axis current and q-axis current of the synchronous motor.

[0145] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0146] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An unmanned forklift stacking method based on synchronous motor weak magnetic control, characterized in that: Including the acquisition of goods and the stacking of goods; The steps to obtain the goods are as follows: Obtain the difference between the height of the cargo and the current height of the fork arm as the first difference; Determine whether the first difference is greater than a height threshold, and if so, generate a first current signal of the synchronous motor; if so, generate a second current signal of the synchronous motor; Inputting the first current signal or the second current signal into the controller so that the height of the fork arm is adjusted to the height of the cargo; The steps for stacking goods are as follows: Obtain the weight of the goods, and then determine whether the weight of the goods is less than the weight threshold. If it is less than the weight threshold, obtain the difference between the current height of the fork arm and the stacking height as the second difference; determining whether the second difference is greater than a height threshold, and if so, generating a first current signal of the synchronous motor; If it is less than the height threshold, a second current signal of the synchronous motor is generated; If it is greater than the weight threshold, a third current signal of the synchronous motor is generated according to the weight of the cargo; The first current signal, the second current signal or the third current signal is input into the controller to adjust the height of the fork arm to the height of the stacking position.

2. The unmanned forklift stacking method based on synchronous motor weak magnetic control according to claim 1 is characterized in that: The first current signal includes a first sub-signal and a second sub-signal; controlling the current of the synchronous motor under the control of the first sub-signal so that the speed of the synchronous motor is increased to a first speed; When the first speed is reached, the current of the synchronous motor is controlled by the second sub-signal.

3. The unmanned forklift stacking method based on synchronous motor weak magnetic control according to claim 2 is characterized in that: The steps for obtaining the current in the first sub-signal are as follows: give the synchronous motor a fixed torque, and obtain the q-axis current I under the fixed torque by the MTPA method. q and the d-axis current I d ; The steps for obtaining the current in the second sub-signal are as follows: Get the given current I of the q axis in real time qRef , the given current I qRef Input to the low-pass filter to get the first parameter I' qRef ; Get the feedback current I of the q axis in real time q , the given current I q Input to the low-pass filter to obtain the second parameter I q '; Get the first parameter I' qRef and the second parameter I′ q The difference E is used as the input of the PI controller to obtain the current feedback given term D1; According to the rated current I n and rated speed ω n Calculate the amplification factor Kc of the feedforward given term of the weakening magnetic current; Obtaining the current magnetic weakening speed increment, adjusting the speed increment by the amplification factor Kc, and obtaining the current feedback given item D2; The d-axis current I is obtained by adding the feedback given term D1 and the feedforward given term D2. d ; The maximum limit value I of the q-axis current is obtained based on the maximum current and the d-axis current. Q .

4. The unmanned forklift stacking method based on synchronous motor weak magnetic control according to claim 1 is characterized in that: The second current signal acquisition method is to give the synchronous motor a fixed torque and obtain the q-axis current I under the fixed torque by the MTPA method. q and the d-axis current I d .

5. The unmanned forklift stacking method based on synchronous motor weak magnetic control according to claim 1 is characterized in that: The steps of generating the third current signal are as follows: Obtain the friction coefficient of the pallet where the goods are located, and obtain the friction force of the pallet on the forklift based on the friction coefficient; Obtaining the torque required by the synchronous motor according to the friction force, the weight of the cargo and the pallet, and the second difference; The required torque is input into the current output model to obtain the required d-axis current and q-axis current of the synchronous motor; The formula for obtaining the required torque is as follows: Where W is the weight of the pallet and the cargo, g is the acceleration due to gravity, F is the friction force, λ is the adjustment coefficient, and r is the conversion factor; The current output model is as follows: Where γ is a constant factor greater than 0, p is the number of pole pairs of the synchronous motor, n is the number of turns per phase winding, ψ is the flux linkage generated by the permanent magnet, and Ld and Lq are the inductances on the d-axis and q-axis of the synchronous motor, respectively.

6. An unmanned forklift stacking system based on synchronous motor weak magnetic control, characterized in that: The method for stacking an unmanned forklift based on weak magnetic control of a synchronous motor according to any one of claims 1 to 5 comprises a cargo acquisition module and a cargo stacking module; The cargo acquisition module is used to obtain the difference between the height of the cargo and the current height of the fork arm as a first difference; Determine whether the first difference is greater than a height threshold, and if so, generate a first current signal of the synchronous motor; if so, generate a second current signal of the synchronous motor; Inputting the first current signal or the second current signal into the controller so that the height of the fork arm is adjusted to the height of the cargo; The cargo stacking module is used to obtain the weight of the cargo, and then determine whether the cargo weight is less than a weight threshold. If it is less than the weight threshold, the difference between the current height of the fork arm and the stacking height is obtained as a second difference; determining whether the second difference is greater than a height threshold, and if so, generating a first current signal of the synchronous motor; If it is less than the height threshold, a second current signal of the synchronous motor is generated; If it is greater than the weight threshold, a third current signal of the synchronous motor is generated; The first current signal, the second current signal or the third current signal is input into the controller to adjust the height of the fork arm to the height of the stacking position.

7. The unmanned forklift stacking system based on synchronous motor weak magnetic control according to claim 6 is characterized in that: The cargo acquisition module includes a first current signal module; The first current signal module is used to control the current of the synchronous motor under the control of the first sub-signal, so that the speed of the synchronous motor is increased to a first speed; When the first speed is reached, the current of the synchronous motor is controlled by the second sub-signal.

8. The unmanned forklift stacking system based on synchronous motor weak magnetic control according to claim 6 is characterized in that: The first current signal module includes a first sub-signal acquisition unit and a second sub-signal acquisition unit; The first sub-signal acquisition unit is used to give the synchronous motor a fixed torque, and obtain the q-axis current I under the fixed torque through the MTPA method. q and the d-axis current I d ; The second sub-signal acquisition unit is used to obtain the given current I of the q axis in real time. qRef , the given current I qRef Input to the low-pass filter to get the first parameter I' qRef ; Get the feedback current I of the q axis in real time q , the given current I q Input to the low-pass filter to obtain the second parameter I' q ; Get the first parameter I q ' Ref With the second parameter I q The difference E of ′ is used as the input of the PI controller to obtain the current feedback given term D1; According to the rated current I n and rated speed ω n Calculate the amplification factor Kc of the feedforward given term of the weakening magnetic current; Obtaining the current magnetic weakening speed increment, adjusting the speed increment by the amplification factor Kc, and obtaining the current feedback given item D2; The d-axis current I is obtained by adding the feedback given term D1 and the feedforward given term D2. d ; The maximum limit value I of the q-axis current is obtained based on the maximum current and the d-axis current. Q .

9. The unmanned forklift stacking system based on synchronous motor weak magnetic control according to claim 6, characterized in that: The cargo stacking module includes a third signal generating unit, which is used to obtain the friction coefficient of the pallet where the cargo is located, and obtain the friction force of the pallet on the forklift according to the friction coefficient; Obtaining the torque required by the synchronous motor according to the friction force, the weight of the cargo and the pallet, and the second difference; The required torque is input into the current output model to obtain the required d-axis current and q-axis current of the synchronous motor.

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