A stacking method and system for unmanned forklifts based on field weakening control of synchronous motors

Abstract

A method for unmanned forklift stacking based on synchronous motor field weakening control is characterized by including the acquisition and stacking of goods. The acquisition steps are as follows: acquiring the difference between the current height of the goods and the current height of the fork arm as a first difference value; determining whether the first difference value is greater than a height threshold; if it is greater than the height threshold, generating a first current signal of the synchronous motor; if it is less than the height threshold, generating a second current signal of the synchronous motor; inputting the first current signal or the second current signal into the controller to adjust the height of the fork arm to the height of the goods. In this invention, different operating parameters are acquired through different sensors to achieve automated and intelligent control of the synchronous motor during goods stacking, which helps to reduce labor costs, improve production efficiency, and enhance the stability of goods transportation during stacking.

Description

Technical Field

[0001] This invention relates to the field of unmanned forklift technology, and in particular to an unmanned forklift stacking method and system based on synchronous motor field weakening control. Background Technology

[0002] With advancements in technology and increased innovation, many companies have adopted automated production lines, enabling large-scale mass production. Due to this increased production volume, companies now need to stack and store finished products in warehouses for subsequent shipment.

[0003] Currently, during palletizing, the motor current input of the unmanned forklift is manually adjusted to raise and lower the fork arm. However, due to the limited human intervention, the adjustment of the lifting switch is based on human experience for goods at different heights and with different weights. This may result in excessive current input, causing the fork arm to vibrate and affecting the stability of palletizing. Summary of the Invention

[0004] To address the aforementioned shortcomings, the present invention aims to propose an unmanned forklift stacking method and system based on synchronous motor field weakening control.

[0005] To achieve this objective, the present invention adopts the following technical solution: an unmanned forklift stacking method based on synchronous motor field weakening control, including the acquisition of goods and the stacking of goods;

[0006] The steps for acquiring the goods are as follows:

[0007] The difference between the height of the goods and the current height of the forklift is obtained as the first difference value;

[0008] Determine whether the first difference is greater than the height threshold. If it is greater than the height threshold, generate the first current signal of the synchronous motor. If it is less than the height threshold, generate the second current signal of the synchronous motor.

[0009] The first current signal or the second current signal is input to the controller to adjust the height of the fork arm to the height of the goods.

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

[0011] If the weight of the goods is obtained, 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 value.

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

[0013] If the weight exceeds the weight threshold, a third current signal for the synchronous motor is generated based on the weight of the goods.

[0014] 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.

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

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

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

[0018] Preferably, the steps for obtaining the current in the first sub-signal are as follows: A fixed torque is applied to the synchronous motor, and the q-axis current I under the fixed torque is obtained using the MTPA method. q and d-axis current I d ;

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

[0020] Real-time acquisition of the given current I along the q-axis qRef , give current I qRef The input is fed into a low-pass filter to obtain the first parameter I′. qRef ;

[0021] Real-time acquisition of q-axis feedback current I q , give current I q The input is fed into a low-pass filter to obtain the second parameter I′. q ;

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

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

[0024] Obtain the current rotational speed increment of the field weakening, and adjust the rotational speed increment through the amplification factor Kc to obtain the current feedback setpoint D2;

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

[0026] The maximum limit value I of the q-axis current is obtained based on the maximum current and the current along the d-axis. Q .

[0027] Preferably, the second current signal acquisition method involves: applying a fixed torque to the synchronous motor and acquiring the q-axis current I under the fixed torque using the MTPA method. q and d-axis current I d .

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

[0029] Obtain the coefficient of friction of the pallet containing the goods, and then calculate the frictional force of the pallet on the forklift based on the coefficient of friction.

[0030] The torque required for the synchronous motor is obtained based on the friction force, the weight of the goods and the pallet, and the second difference.

[0031] Input the required torque 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 due to gravity, F is the friction force, λ is the adjustment coefficient, and r is the conversion factor;

[0035] The specific 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 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.

[0038] An unmanned forklift stacking system based on synchronous motor field weakening control, using the aforementioned unmanned forklift stacking method based on synchronous motor field weakening control, includes a goods acquisition module and a goods stacking module;

[0039] The cargo acquisition module is used to obtain the difference between the height of the cargo and the current height of the forklift, as the first difference value;

[0040] Determine whether the first difference is greater than the height threshold. If it is greater than the height threshold, generate the first current signal of the synchronous motor. If it is less than the height threshold, generate the second current signal of the synchronous motor.

[0041] The first current signal or the second current signal is input to the controller to adjust the height of the fork arm to the height of the goods.

[0042] The cargo stacking module is used to obtain the weight of the cargo, and then determine whether the weight of the cargo 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 value.

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

[0044] If the weight exceeds the threshold, a third current signal for the synchronous motor is generated.

[0045] 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.

[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 the first speed;

[0048] Once 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 provide the synchronous motor with a fixed torque and obtain the q-axis current I under the fixed torque using the MTPA method. q and d-axis current I d ;

[0051] The second sub-signal acquisition unit is used to acquire the given current I along the q-axis in real time. qRef , give current I qRef The input is fed into a low-pass filter to obtain the first parameter I′. qRef ;

[0052] Real-time acquisition of q-axis feedback current I q , give current I q The input is fed into a low-pass filter to obtain the second parameter I′. q ;

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

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

[0055] Obtain the current rotational speed increment of the field weakening, and adjust the rotational speed increment through the amplification factor Kc to obtain the current feedback setpoint D2;

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

[0057] The maximum limit value I of the q-axis current is obtained based on the maximum current and the current along the d-axis. Q .

[0058] Preferably, the cargo stacking module includes a third signal generation unit, which is used to obtain the friction coefficient of the pallet on which the cargo is located, and to obtain the friction force of the pallet on the forklift based on the friction coefficient.

[0059] The torque required for the synchronous motor is obtained based on the friction force, the weight of the goods 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 this invention, different operating parameters are obtained by different sensors, so as to realize the automated and intelligent control of the synchronous motor when the goods are being stacked, which helps to reduce labor costs, improve production efficiency and the stability of goods transportation during stacking. Attached Figure Description

[0062] Figure 1 This is a flowchart illustrating the acquisition of goods in one embodiment of the method of the present invention.

[0063] Figure 2 This is a flowchart of cargo stacking in one embodiment of the method of the present invention.

[0064] Figure 3 This is a schematic diagram of the structure of one embodiment of the system of the present invention. Detailed Implementation

[0065] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0066] In the description of embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0068] like Figures 1-3 As shown, an unmanned forklift stacking method based on synchronous motor field weakening control includes the acquisition of goods and the stacking of goods.

[0069] The steps for acquiring the goods are as follows:

[0070] The difference between the height of the goods and the current height of the forklift is obtained as the first difference value;

[0071] Determine whether the first difference is greater than the height threshold. If it is greater than the height threshold, generate the first current signal of the synchronous motor. If it is less than the height threshold, generate the second current signal of the synchronous motor.

[0072] The first current signal or the second current signal is input to the controller to adjust the height of the fork arm to the height of the goods.

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

[0074] If the weight of the goods is obtained, 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 value.

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

[0076] If the weight exceeds the weight threshold, a third current signal for the synchronous motor is generated based on the weight of the goods.

[0077] 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.

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

[0079] When retrieving goods, the fork arm is raised or lowered to the corresponding height. Since there are no goods in the fork arm at this time, the influence of the weight of the goods on the output of the synchronous motor does not need to be considered. Only the 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, thus causing the synchronous motor to enter the field weakening control stage. Therefore, when retrieving 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, the weight of the goods on the forks needs to be considered. Therefore, it's necessary to determine if the weight is less than a weight threshold. If it is, the weight's impact on the motor is negligible, and the second difference is used to generate different currents. However, if the weight exceeds the threshold, a third current signal for the synchronous motor needs to be generated based on the weight. This invention considers the impact of goods weight on the current input to the synchronous motor, thereby improving the stability of the forklift during goods stacking.

[0081] This invention uses different sensors to acquire different operating parameters, enabling automated and intelligent control of the synchronous motor during palletizing, which helps reduce labor costs, improve production efficiency, and enhance the stability of goods transportation during palletizing.

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

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

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

[0085] Since the height adjustment distance of the forklift arm is relatively long when the first difference is greater than the height difference, after adjusting the current using the traditional MTPA method, the speed of the synchronous motor will reach the first speed (turning speed). At this time, the synchronous motor enters the field weakening control stage. At this time, it is necessary to generate the d-axis current and q-axis current in the field weakening control through the second sub-signal, so as to achieve stable lifting and lowering of the forklift arm.

[0086] Preferably, the steps for obtaining the current in the first sub-signal are as follows: A fixed torque is applied to the synchronous motor, and the q-axis current I under the fixed torque is obtained using the MTPA method. q and d-axis current I d ;

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

[0088] Real-time acquisition of the given current I along the q-axis qRef , give current I qRef The input is fed into a low-pass filter to obtain the first parameter I′. qRef ;

[0089] Real-time acquisition of q-axis feedback current I q , give current I q The input is fed into a low-pass filter to obtain the second parameter I′. q ;

[0090] By acquiring the given and feedback currents of the q-axis in real time and processing them using a low-pass filter, more stable and accurate current parameters can be obtained. This method helps to precisely control the operation of synchronous motors, improving stability and reliability.

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

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

[0093] The formula for obtaining the current feedback reference 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 These are the proportional gain coefficient and 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 term of the field weakening current is calculated. The amplification factor Kc is determined based on the rated current and rated speed of the motor. By adjusting the speed increment through the amplification factor Kc, the motor can be ensured to operate in a high-efficiency and stable state.

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

[0098]

[0099] Where I n Rated current, ω n Rated speed;

[0100] Obtain the current rotational speed increment of the field weakening, and adjust the rotational speed increment through the amplification factor Kc to obtain the current feedback setpoint D2;

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

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

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

[0104] The maximum limit value I of the q-axis current is obtained based on the maximum current and the current along the d-axis. Q .

[0105]

[0106] Where I max For maximum output current, I d The current is along the d-axis.

[0107] When adjusting the q-axis current, the maximum limit value I can be selected. Q As the current of the q-axis, this can increase the speed of the synchronous motor while ensuring stable operation, and accelerate the fork arm to reach the height of the goods.

[0108] Preferably, the second current signal acquisition method involves: applying a fixed torque to the synchronous motor and acquiring the q-axis current I under the fixed torque using the MTPA method. q and d-axis current I d .

[0109] Since the torque supplied to the synchronous motor is fixed, the displacement distance (height threshold) of the fork arm when the synchronous motor reaches the first speed is fixed. Therefore, when the second current signal is used to determine the current, the synchronous motor has not yet entered the field weakening control stage. Thus, the method of obtaining the second current signal is the same as the method of obtaining the current in the first sub-signal.

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

[0111] Obtain the coefficient of friction of the pallet containing the goods, and then calculate the frictional force of the pallet on the forklift based on the coefficient of friction.

[0112] When the weight of the goods exceeds a certain weight threshold, a synchronous motor needs to output a certain torque to achieve the lifting and lowering of the forklift arms. Therefore, this invention accurately predicts the frictional force of the pallet on the forklift by precisely calculating the friction coefficient of the pallet. This helps the forklift move the pallet and the goods on it more smoothly during handling or lifting. It avoids generating excessive torque, which could lead to insufficient friction causing the pallet to slide or shake on the forklift arms, thus ensuring transportation stability and the safety of the goods.

[0113] The torque required for the synchronous motor is obtained based on the friction force, the weight of the goods and the pallet, and the second difference.

[0114] Input the required torque 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 due to gravity, F is the friction force, λ is the adjustment coefficient, and r is the conversion factor;

[0118] The specific 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 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.

[0121] Once the required torque for the motor is known, it can be input into the current output model, which limits the sum of the q-axis current and the d-axis current to a minimum. This ensures stable lifting of the fork arm while maximizing energy efficiency and reducing unnecessary power consumption, meeting the requirements of green and energy-saving modern production.

[0122] An unmanned forklift stacking system based on synchronous motor field weakening control, using the aforementioned unmanned forklift stacking method based on synchronous motor field weakening control, includes a goods acquisition module and a goods stacking module;

[0123] The cargo acquisition module is used to obtain the difference between the height of the cargo and the current height of the forklift, as the first difference value;

[0124] Determine whether the first difference is greater than the height threshold. If it is greater than the height threshold, generate the first current signal of the synchronous motor. If it is less than the height threshold, generate the second current signal of the synchronous motor.

[0125] The first current signal or the second current signal is input to the controller to adjust the height of the fork arm to the height of the goods.

[0126] The cargo stacking module is used to obtain the weight of the cargo, and then determine whether the weight of the cargo 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 value.

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

[0128] If the weight exceeds the threshold, a third current signal for the synchronous motor is generated.

[0129] 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.

[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 the first speed;

[0132] Once 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 provide the synchronous motor with a fixed torque and obtain the q-axis current I under the fixed torque using the MTPA method. q and d-axis current I d ;

[0135] The second sub-signal acquisition unit is used to acquire the given current I along the q-axis in real time. qRef , give current I qRef The input is fed into a low-pass filter to obtain the first parameter I′. qRef ;

[0136] Real-time acquisition of q-axis feedback current I q , give current I q The input is fed into a low-pass filter to obtain the second parameter I. q ′;

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

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

[0139] Obtain the current rotational speed increment of the field weakening, and adjust the rotational speed increment through the amplification factor Kc to obtain the current feedback setpoint D2;

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

[0141] The maximum limit value I of the q-axis current is obtained based on the maximum current and the current along the d-axis. Q .

[0142] Preferably, the cargo stacking module includes a third signal generation unit, which is used to obtain the friction coefficient of the pallet on which the cargo is located, and to obtain the friction force of the pallet on the forklift based on the friction coefficient.

[0143] The torque required for the synchronous motor is obtained based on the friction force, the weight of the goods 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 references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

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

Claims

1. A stacking method for unmanned forklifts based on field weakening control of synchronous motors, characterized in that, This includes the acquisition and stacking of goods; The steps for acquiring the goods are as follows: The difference between the height of the goods and the current height of the forklift is obtained as the first difference value; Determine whether the first difference is greater than the height threshold. If it is greater than the height threshold, generate the first current signal of the synchronous motor. If it is less than the height threshold, generate the second current signal of the synchronous motor. The first current signal or the second current signal is input to the controller to adjust the height of the fork arm to the height of the goods. The steps for stacking goods are as follows: If the weight of the goods is obtained, 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 value. Determine if the second difference is greater than the height threshold. If it is greater than the height threshold, generate the first current signal of the synchronous motor. If the height is less than the threshold, a second current signal for the synchronous motor is generated. If the weight exceeds the weight threshold, a third current signal for the synchronous motor is generated based on the weight of the goods. 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; The first current signal includes a first sub-signal and a second sub-signal; The current of the synchronous motor is controlled under the control of the first sub-signal, so that the speed of the synchronous motor is increased to the first speed; Once the first speed is reached, the current of the synchronous motor is controlled by the second sub-signal; The steps for obtaining the current in the first sub-signal are as follows: A fixed torque is applied to the synchronous motor, and the q-axis current under the fixed torque is obtained using the MTPA method. and d-axis current ; The steps for obtaining the current in the second sub-signal are as follows: Real-time acquisition of the given current along the q-axis , give current The input is fed into a low-pass filter to obtain the first parameter. ; Real-time acquisition of q-axis feedback current , give current The input is fed into a low-pass filter to obtain the second parameter. ; Get the first parameter With the second parameter The difference E is used as the input of the PI controller to obtain the current feedback setpoint D1; According to the rated current and rated speed Calculate the amplification factor Kc of the feedforward term of the field weakening current; Obtain the current rotational speed increment of the field weakening, and adjust the rotational speed increment through the amplification factor Kc to obtain the current feedforward given term D2; The d-axis current is obtained by adding the feedback reference D1 and the feedforward reference D2. ; The maximum limit value of the q-axis current is obtained based on the maximum current and the current along the d-axis. .

2. The unmanned forklift stacking method based on synchronous motor field weakening control according to claim 1, characterized in that, The second current signal acquisition method: A fixed torque is applied to the synchronous motor, and the q-axis current under the fixed torque is obtained using the MTPA method. and d-axis current .

3. The unmanned forklift stacking method based on synchronous motor field weakening control according to claim 1, characterized in that, The steps for generating the third current signal are as follows: Obtain the coefficient of friction of the pallet containing the goods, and then calculate the frictional force of the pallet on the forklift based on the coefficient of friction. The torque required for the synchronous motor is obtained based on the friction force, the weight of the goods and the pallet, and the second difference. Input the required torque 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 goods, g is the acceleration due to gravity, and F is the frictional force. r is the adjustment coefficient, and r is the conversion factor; The specific current output model is as follows: ； in is a constant factor greater than 0, p is the number of pole pairs of the synchronous motor, and n is the number of turns per phase winding. The flux linkage generated by the permanent magnet, Ld, and Lq are the inductances on the d-axis and q-axis of the synchronous motor, respectively. and The q-axis current and d-axis current under a fixed torque are obtained by the MTPA method, respectively.

4. An unmanned forklift stacking system based on synchronous motor field weakening control, characterized in that, The unmanned forklift stacking method based on synchronous motor field weakening control according to any one of claims 1 to 3 includes 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 forklift, as the first difference value; Determine whether the first difference is greater than the height threshold. If it is greater than the height threshold, generate the first current signal of the synchronous motor. If it is less than the height threshold, generate the second current signal of the synchronous motor. The first current signal or the second current signal is input to the controller to adjust the height of the fork arm to the height of the goods. The cargo stacking module is used to obtain the weight of the cargo, and then determine whether the weight of the cargo 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 value. Determine if the second difference is greater than the height threshold. If it is greater than the height threshold, generate the first current signal of the synchronous motor. If the height is less than the threshold, a second current signal for the synchronous motor is generated. If the weight exceeds the threshold, a third current signal for 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.

5. The unmanned forklift stacking system based on synchronous motor field weakening control according to claim 4, 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 the first speed; Once the first speed is reached, the current of the synchronous motor is controlled by the second sub-signal.

6. The unmanned forklift stacking system based on synchronous motor field weakening control according to claim 5, 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 provide the synchronous motor with a fixed torque and obtain the q-axis current under the fixed torque using the MTPA method. and d-axis current ; The second sub-signal acquisition unit is used to acquire the given current of the q-axis in real time. , give current The input is fed into a low-pass filter to obtain the first parameter. ; Real-time acquisition of q-axis feedback current , give current The input is fed into a low-pass filter to obtain the second parameter. ; Get the first parameter With the second parameter The difference E is used as the input of the PI controller to obtain the current feedback setpoint D1; According to the rated current and rated speed Calculate the amplification factor Kc of the feedforward term of the field weakening current; Obtain the current rotational speed increment of the field weakening, and adjust the rotational speed increment through the amplification factor Kc to obtain the current feedforward given term D2; The d-axis current is obtained by adding the feedback reference D1 and the feedforward reference D2. ; The maximum limit value of the q-axis current is obtained based on the maximum current and the current along the d-axis. .

7. The unmanned forklift stacking system based on synchronous motor field weakening control according to claim 4, characterized in that, The cargo stacking module includes a third signal generation unit, which is used to obtain the friction coefficient of the pallet on which the cargo is located, and to obtain the friction force of the pallet on the forklift based on the friction coefficient. The torque required for the synchronous motor is obtained based on the friction force, the weight of the goods 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.

Images