A Method for Controlling the Lateral Contact Force of a Direct-Drive Scroll Machine

Abstract

Lateral contact force control method for direct-drive scroll machine of the present invention: S1. Read the variable information of the orbiting scroll of the scroll machine in the XY coordinate system and map it to the n-t coordinate system to obtain the current v t , s n , f cn ; S2. Given the desired f dn , add it to f cn to generate a revised amount of position #imgabs0# S3. #imgabs1# is added to the desired position #imgabs2# to generate a position reference value #imgabs3# S4. #imgabs4# is added to the actual position s n to generate a deviation value #imgabs5# S5. #imgabs6# obtains the current component i qn through position closed-loop control; S6. Given the tangential reference velocity #imgabs7# and add it to the current v t to generate a deviation value #imgabs8# S7. #imgabs9# obtains the current component i qt through velocity closed-loop control; S8. The current components i qn , i qt in the n-t coordinate system are transformed through coordinates to obtain the current components i qx , i qy in the XY coordinate system; S9. According to the current components obtained in S8, the motor drives the orbiting scroll to move; S10. Judge whether the normal desired contact force f dn is reached. If so, return to S1; if not, execute S11; S11. Judge whether the contact force is too large or too small. If not, return to S1; if so, stop.

Description

Technical Field

[0001] The present invention belongs to the technical field of dynamic seal control of scroll machines, and particularly relates to a method for controlling the lateral contact force of a direct-drive scroll machine. Background Art

[0002] The scroll machine is a new type of positive-displacement compressor developed in the 1980s, and its core components are a moving scroll and a stationary scroll. The profiles of the moving scroll and the stationary scroll of the scroll machine are the same, and the two are installed with a 180° phase rotation to form several closed crescent-shaped working chambers, and the gas is compressed by the volume change of each working chamber.

[0003] Scroll compressors generally adopt clearance seals. This technology can increase the reliability of scroll compressors. However, too large a clearance will cause unnecessary leakage, and too small a clearance will prevent the parts from operating properly, which hinders the development of scroll compressors in the direction of high pressure and large capacity.

[0004] In order to solve the leakage problem during the operation of scroll machines, many scholars at home and abroad have proposed leakage models and sealing solutions for scroll machines in recent years. For example, Chen Rong et al. established tangential leakage models and radial leakage models, and studied the leakage losses and compression efficiency laws under different clearances. Zha Haibin et al. topologically modeled the geometric model for an actual scroll compressor prototype and used a composite grid construction method to establish a CFD model to model gas leakage. Wang Jianji et al. studied and compared three sealing structures, namely, the smooth clearance seal at the tooth tip of the scroll tooth, the labyrinth seal at the tooth tip, and the combined seal at the tooth tip, and finally proposed a new type of radial combined seal structure. Li Haisheng et al. performed finite element analysis on the polytetrafluoroethylene sealing strip at the tooth tip of the scroll, providing a new method for the design of the sealing strip. Ye Jian et al. proposed a tangential seal structure to reduce leakage and improve the pressurization process for the tangential leakage of the compressor.

[0005] The above research solutions for scroll machine seals all start from the structure and materials, belonging to passive seal solutions. The mechanical coupling between the moving and stationary scrolls is relatively tight, and the calculation and modeling are relatively complex. Aiming at the shortcomings of passive seal solutions, Yan Xilong et al. proposed a control method for active seal of scroll compressors, established databases of the translational trajectories of the moving scroll in cold and hot states respectively, and realized the lateral seal of the scroll machine according to the trajectory points in the database. However, from the perspective of contact force, this method still belongs to open-loop control, and there is still a problem that the contact force is difficult to control.

[0006] None of the above research work has deeply analyzed the contact force during the operation of the scroll machine. The dynamic scroll disk and the static scroll disk remaining in contact is a necessary condition for the normal operation of the scroll machine. Otherwise, gas leakage will occur, affecting the working efficiency of the scroll machine. However, excessive contact pressure between the scroll disks will lead to over-friction phenomena, affecting the service life of the scroll machine. Therefore, it is very important to control the contact force between the scroll disks within a reasonable range, which poses a new challenge to the research on force control.

[0007] When objects come into contact with each other, in order to comply with environmental constraints, it is also necessary to precisely control the contact force between objects to avoid damage to the objects caused by excessive impact force. Compliant control can achieve effective control of force. Compliant control can be divided into active compliant control and passive compliant control. The method of passively adjusting the contact force by installing devices with compliant control functions (such as springs, cylinders, dampers, etc.) between objects is called passive compliant control. This method requires adding additional passive compliant devices and does not have control capabilities, which does not match the working conditions of the scroll machine. Active compliance is to actively control the interaction force between objects according to force feedback information. Compared with passive control, although active control omits some mechanical devices and reduces the coupling degree, the design requirements for the controller become higher after removing these constraints. In the research on active compliant controllers, Kazuo Kiguchi et al. designed a force-position hybrid controller based on a fuzzy neural network for polishing tasks in unknown environments; Jonas Buchli et al. used variable impedance control based on reinforcement learning for complex environmental machining tasks.

[0008] Gholamreza Nazmara et al. designed a fuzzy controller based on the gradient descent method to adjust the parameters of the impedance controller for trajectory planning in an environment with obstacles.

[0009] The above research has proposed corresponding compliant control methods for unknown environments respectively. The control accuracy of the control method based on fuzzy rules is limited, and the reinforcement learning method requires multiple experiments to obtain the optimal control parameters, which affects the operation of the equipment. However, there is no corresponding compliant control solution for the parameter coupling problem existing in the modeling process of the lateral seal arc control of the scroll machine. The technical problems existing in the above existing research are summarized as follows:

[0010] 1. Most of the existing technologies are passive sealing solutions. These solutions only start from the structure and materials, with high calculation and design difficulties, high requirements for materials, or they will lead to the complication of the structure and installation process, resulting in high costs and complex maintenance work. Moreover, it is difficult to adapt flexibly when the working conditions change.

[0011] 2. Some existing active sealing methods have established databases of the translational trajectories of the moving scroll under cold and hot conditions respectively in response to the shortcomings of the passive sealing solution, and achieve the lateral sealing of the scroll compressor based on the trajectory points in the database. However, such methods currently require the establishment of an offline database, do not directly address the problem of lateral sealing of the scroll compressor by taking the contact force as the entry point, and do not propose solutions to the parameter coupling problem existing in the process of modeling the lateral sealing of the scroll compressor. Summary of the Invention

[0012] In view of the above problems existing in the existing scroll compressors, the present invention proposes a compliant control method for the lateral contact force of a scroll compressor with dynamic coordinate transformation to achieve the control of the contact force between the moving scroll and the stationary scroll.

[0013] The present invention adopts the following technical solutions:

[0014] A method for controlling the lateral contact force of a direct-drive scroll compressor, comprising the following steps:

[0015] S1. Read the variable information v x , v y , s x , s y , f cx , f cy of the moving scroll of the scroll compressor after the motor runs, and perform coordinate transformation to map to the normal-tangential coordinate system, i.e., the n-t coordinate system, to obtain the current velocity

[0016] v t , the actual position s n , and the current contact force f cn ; wherein, v x , v y are velocity components, s x , s y are positions, and f cx , f cy are thrusts;

[0017] S2. Given a desired normal contact force f dn , which is superimposed with the current contact force f cn , and a position correction amount is generated through an impedance controller

[0018] S3. The position correction amount is superimposed with the desired position to generate a position reference value

[0019] S4. The position reference value is superimposed with the actual position s n to generate a deviation value

[0020] S5. Deviation value The current component i is obtained through position closed-loop control qn ;

[0021] S6. A tangential reference speed is given which is superimposed with the current speed v t to generate a deviation value

[0022] S7. Deviation value The current component i is obtained through speed closed-loop control qt ;

[0023] S8. The current components i qn , i qt in the normal-tangential coordinate system are transformed through coordinate transformation to obtain the current components i qx , i qy in the XY coordinate system;

[0024] S9. According to the current components obtained in step S8, the motor drives the orbiting scroll of the scroll compressor to move;

[0025] S10. Determine whether the normal desired contact force f dn is reached. If so, return to step S1; if not, execute step S11;

[0026] S11. Determine whether the contact force is too large or too small to cause a failure. If not, return to step S1; if so, stop.

[0027] Preferably, in step S1, when transforming from the XY coordinate system to the normal-tangential coordinate system, the specific transformation of the variable information is as follows:

[0028] The projection of the speed during the translational motion of the orbiting scroll in the n-t coordinate system forms two components, normal and tangential. Among them, the normal component v n >0 indicates that the translational radius increases, and vice versa; the tangential component v t >0 indicates that the translation is in the counterclockwise direction, and vice versa, the translation is in the clockwise direction;

[0029] Define the speed components v x , v y in the XY coordinate system and the speed components v n , v t in the n-t coordinate system are related as shown in Equation (7):

[0030]

[0031] The thrust force received by the moving scroll is generated by the motor, and the thrust force is related to the q-axis current of the motor; the q-axis current of the X-axis motor is denoted as i qx ; the q-axis current of the Y-axis motor is denoted as i qy ; define i qx and i qy and the current components i qn and i qt in the n-t coordinate system are related as shown in Equation (8):

[0032]

[0033] Define the components f cx and f cy of the contact force received when the moving scroll contacts the stationary scroll of the scroll machine in the XY coordinates, and the components f cn and f ct in the n-t coordinates are related as shown in Equation (9):

[0034]

[0035] The moving scroll is only affected by the thrust force generated by the motor and the contact force after contacting the stationary scroll. Therefore, the relationship between the speed and force of the moving scroll is expressed by Equation (10):

[0036]

[0037] In Equation (10), k f is the thrust coefficient of the linear motor; m is the mass of the moving scroll, and both are constants;

[0038] Multiply both sides of Equation (10) by the expression of the coordinate transformation matrix as shown in Equation (11):

[0039]

[0040] The derivative of the coordinate transformation matrix involves the derivative of θ with respect to time, and the relationship between θ, displacement, and speed is expressed as follows:

[0041]

[0042] After differentiating Equation (7) and combining with Equations (11) and (12), the relationship between the displacement, speed, and thrust variables of the particle in the n-t coordinates is obtained,

[0043]

[0044] The relationship between the normal displacement s n and the normal speed v n is expressed as:

[0045]

[0046] Preferably, in step S2, the impedance controller generates a revised amount of the position The specific process is as follows: A desired normal contact force f dn is superimposed with the current contact force f cn During the contact process between the moving and static scroll disks, the contact force may be too large or too small. To effectively control the force, an impedance controller is introduced to correct the deviation of the contact force (based on the difference between the desired normal contact force f dn and the current contact force f cn as the input of the compliance controller, and after the action of the impedance controller, a revised amount of the position is output. Finally, through the position closed-loop and coordinate transformation in step S5, the current contact force is continuously adjusted to reach the desired contact force magnitude), thereby generating a revised amount of the position.

[0047] Preferably, in step S5, the closed-loop control is specifically as follows: The position reference value is superimposed with the actual position s n to generate a position deviation value By adjusting the parameters of the PD closed-loop controller (according to the formula M is the desired inertia coefficient, w n affects the stability of the closed-loop control system, ε affects the overshoot magnitude of the system, k p and k d being too large or too small will cause system instability and excessive overshoot. By continuously adjusting the parameters k p and k d , the stability of the system is improved while reducing the overshoot of the system), the output is i qn , i qn obtains s n through the integral link, and the position quantity is corrected through the position closed-loop control.

[0048] Preferably, in step S7, the closed-loop control is specifically as follows: The speed reference value is superimposed with the actual speed v t to generate a speed deviation value By adjusting the parameters of the PI closed-loop controller, the output is i qt , i qt outputs v t through the integral link, and the speed quantity is corrected through the speed closed-loop.

[0049] Preferably, in step S7, the adjustment of the parameters of the PI closed-loop controller is specifically as follows: According to the formula M is the desired inertia coefficient, w n affects the stability of the closed-loop control system, ε affects the overshoot magnitude of the system, and the parameter kp and k i being too large or too small will cause system instability and excessive overshoot. By continuously adjusting the parameters k p and k i , the stability of the system is improved while the overshoot of the system is reduced.

[0050] Preferably, in step S8, the current components i qn , i qt in the normal-tangential coordinate system are transformed into the current components i qn , i qt in the XY coordinate system through coordinate transformation. The specific process is as follows: According to the transformation relation for transforming the XY coordinate system to the normal-tangential coordinate system and the defined i qx , i qy and the relationship qn between i qt and the current components i in the n-t coordinate system, the transformation of the current components from the normal-tangential coordinate system to the XY coordinate system is realized.

[0051] Compared with the prior art, the present invention has the following technical effects:

[0052] When the control method of the present invention is used to realize the lateral seal of the scroll machine, the structure and installation process can be simplified, the cost is reduced, the calculation and design difficulty are reduced, the service life of the scroll machine is extended, and it can more flexibly adapt to the special working conditions of the scroll machine. The control method of the present invention can actively control the low contact force between the moving and static scroll plates during the operation of the scroll machine, reduce mechanical wear, and thus achieve high sealing performance.

[0053] The present invention solves the problem of lateral leakage during the operation of the scroll compressor, and solves the problems of complex structure, high cost, and short service life of the passive seal scheme of the scroll compressor; the present invention also solves the problems of mechanical wear and gas leakage caused by excessive contact force between the moving and static scroll plates in the active seal control method of the scroll machine, which reduces the working efficiency of the scroll machine, and solves the problem of multi-parameter coupling existing in the lateral seal modeling process of the scroll machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is a schematic diagram of the position of the moving scroll plate. (a) The moving scroll plate is not in contact with the static scroll plate; (b) The moving scroll plate is just in contact with the static scroll plate; (c) The moving scroll plate is over-contacted with the static scroll plate.

[0055] Figure 2 is a schematic diagram of the relationship between the contact force between objects and the position. (a) The objects are not in contact; (b) The objects are over-contacted.

[0056] Figure 3 is a basic block diagram of compliant control.

[0057] Figure 4 It is a schematic diagram of compliant control in the XY coordinate system. (a) Schematic diagram of control on the x-axis; (b) Schematic diagram of control on the y-axis.

[0058] Figure 5 It is a schematic diagram of the positional relationship of the coordinate system.

[0059] Figure 6 It is a schematic diagram of the normal-tangential components of the contact force.

[0060] Figure 7 It is a block diagram of compliant control after coordinate transformation.

[0061] Figure 8 It is a block diagram of the controller. (a) Schematic diagram of control of the normal part; (b) Schematic diagram of control of the tangential part.

[0062] Figure 9 It is the overall control diagram of the lateral dynamic seal control of the scroll machine based on the normal-tangential dynamic coordinate system.

[0063] Figure 10 It is the overall flowchart of the lateral contact force control of the direct-drive scroll machine.

[0064] Figure 11 It is a schematic diagram of the working platform of the direct-drive scroll machine.

[0065] Figure 11 In it, 1 - stationary scroll disk, 2 - moving scroll disk, 3 - two-dimensional grating reading head, 4 - two-dimensional grating code disk, 5 - permanent magnet, 6 - motor coil winding in the X direction, 7 - motor coil winding in the Y direction. Specific implementation manner

[0066] The following will make a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings.

[0067] The schematic diagram of the working platform of the direct-drive scroll machine is as Figure 11 shown. The linear motor platform in the figure is composed of two spliced linear motors, which can respectively perform movements in the X direction and the Y direction, so as to control the moving scroll disk to operate with two degrees of freedom in the XY directions.

[0068] 1. Representation of the movement space of the moving scroll disk

[0069] The profile curve of the scroll disk is an involute of a circle. Analyzing that the moving scroll disk is at a certain translational trajectory point means that there is at least one point of meshing between the moving scroll disk and the stationary scroll disk. By analyzing the contact point, the equations of the inner and outer walls of the scroll disk profile are rotated and transformed, and it is found that the relative positions between the tangent points before and after the transformation remain unchanged, which means that at any angle of rotation transformation, the distance between the origin and the translational trajectory point is equal. Therefore, a conclusion can be drawn: the translational trajectory of the moving scroll disk is circular. To simplify the subsequent analysis, the moving scroll disk is regarded as a particle, and its position space is as Figure 1 shown.

[0070] Figure 1 In (a), the moving scroll disk is located inside the circle, and at this time, the moving scroll disk does not contact the stationary scroll disk; Figure 1 In (b), the moving scroll disk is located on the circular boundary, and at this time, the moving scroll disk just contacts the stationary scroll disk; Figure 1 In (c), the moving scroll disk is located outside the circle, and at this time, the moving scroll disk has contacted the stationary scroll disk, and the stationary scroll disk will deform to generate a contact force on the moving scroll disk.

[0071] In the ideal state, the moving scroll disk should be located on the circular boundary and perform translation around the circular boundary. The position of the moving scroll disk is controlled by the combination of two degrees of freedom of the XY linear motor.

[0072] 2. Principle of Static Coordinate Compliance Control

[0073] The relationship between the contact force and the position between objects is as Figure 2 shown, where x represents the current position of the object; x0 represents the critical contact position. Figure 2 In (a), x < x0, and at this time, the objects are not in contact, and the contact force is 0; Figure 2 In (b), x > x0, and at this time, the objects have been in contact, and the contact force f c is related to the deformation of the stressed object. Generally, the contact model is represented by a spring model, so Figure 2 the relationship between x, x0, and f c in (b) is shown in Equation (1):

[0074] f c = k0(x - x0) (1)

[0075] In Equation (1), k0 is the stiffness coefficient of the contacting objects, and k0 > 0 is satisfied.

[0076] Combining the above analysis, the block diagram of classical compliance control can be represented by Figure 3 where x d is the expected value of the position; x * is the position reference value required by the position regulator; x is the current position value; x0 is the critical contact position; f c is the feedback signal of the current contact force; fd The desired contact force for the object.

[0077] Assume that the object is in an over-contact state at this time. From Figure 3 it can be deduced that the relationship between f c and f d ,x d ,x0 is as shown in Equation (2):

[0078]

[0079] In Equation (2):

[0080] G(s) = k0

[0081] Z(s) = (Ms 2 + Bs + k) -1

[0082] where Z(s) is the expression form of the impedance controller in the complex frequency domain (i.e., the s-domain), corresponding to the variable form after Laplace transform; M represents the desired inertia coefficient; B represents the desired damping coefficient; k represents the desired stiffness coefficient, and f C (s), f d (s), x d (s), x0(s) are the corresponding variable forms of the variables f c , f d , x d , x0 after Laplace transform respectively; generally, G M (s) is regarded as a low-pass filter.

[0083] Decompose the two-degree-of-freedom planar motion of the moving scroll on the XY linear motor platform into 2 independent one-dimensional motions, and respectively use the classical compliant control method. Then project variables such as the current position and the critical contact position of the moving scroll onto the XY coordinate axes, as Figure 4 shown.

[0084] During the translational motion of the moving scroll around the circumference, x0 and y0 are sinusoidal signals that change with time; f dx , f dy and x d , y d should also be set as sinusoidal signals, which means that the desired contact force and the critical contact position are not constants. In addition, Figure 4 the value of f cx in (a) is related not only to x, x0 but also to y; Figure 4 the value of f cy in (b) is related not only to y, y0 but also to x. This makes it difficult to calculate the contact force in the XY coordinates. Therefore, it is necessary to select an appropriate coordinate transformation to simplify the calculation.

[0085] 3. Principle of Compliant Control for the Normal-Tangential Dynamic Coordinate System of the Tooth Profile

[0086] The XY coordinate system is transformed into the normal-tangential coordinate system, which is hereinafter referred to as the n-t coordinate system. The transformation relationship between them is shown in Equation (3).

[0087]

[0088] In Equation (3), θ can be expressed by Equation (4), where x and y are the positions of the mass point in the XY coordinate system.

[0089] θ = arctan2(y, x) (4)

[0090] The positional relationship between the two coordinate systems is as Figure 5 shown. Where p is the position of the mass point.

[0091] The moving scroll disk is denoted as (s x , s y ) in the XY coordinate system, and the position when it just comes into contact with the stationary scroll disk is denoted as (s x0 , s y0 ). In the n-t coordinate system, the current position of the moving scroll disk is denoted as (s n , s t ), and the position at contact is denoted as (s n0 , s t0 ). The relationship between (s n , s t ) and (s x , s y ) can be expressed by Equation (5):

[0092]

[0093] The value of s n represents the distance from the coordinate origin to the mass point, and there is s n ≥0, s t = 0 always holds. Therefore, in the n-t coordinate system, only the value of s n needs to be concerned about.

[0094] Since the set of all position points where the moving scroll disk just comes into contact with the stationary scroll disk is a circle, the values of these position points are all equal in the n-t coordinate system. They are uniformly denoted as s n0 , and s n0 is equal to the radius r of the circle. The relationship between the displacement vector s n and the normal contact force received is as follows:

[0095]

[0096] Therefore, the expected position and the expected normal contact force f cn can be set as constants. After the n-t coordinate transformation, the classical compliance control method can be used to control the normal contact force between the moving scroll and the stationary scroll.

[0097] Figure 7 is the compliance control block diagram in the n-t coordinate system. Different from Figure 3 : Figure 3 the variables in Figure 7 take XY as the reference coordinate system, while the variables in

[0098] 4. Lateral dynamic seal control method of scroll machine based on normal-tangential dynamic coordinate system

[0099] Based on the n-t coordinate system, describe the motion control method of the moving scroll and the compliance control method in this coordinate system.

[0100] 4.1 Motion variable transformation method of normal-tangential dynamic coordinate system

[0101] Before designing the controller, it is necessary to know the relationship between variables such as the displacement, velocity, and thrust of the particle in the n-t coordinates.

[0102] The velocity during the translational motion of the moving scroll projects into normal and tangential components in the n-t coordinate system. Among them, the normal component v n >0 means that the translational radius increases, and vice versa; the tangential component v t >0 means that the translation is in the counterclockwise direction, and vice versa, the translation is in the clockwise direction.

[0103] Define the velocity components v x , v y in the XY coordinate system and the velocity components v n , v t in the n-t coordinate system, and their relationship is shown in Equation (7):

[0104]

[0105] The thrust received by the moving scroll is generated by the linear motor, and the magnitude of the thrust is related to the q-axis current of the linear motor. The q-axis current of the X-direction linear motor is denoted as i qx , and the q-axis current of the Y-direction linear motor is denoted as i qy . Define i qx , i qy and the current components i qn , iqt The relationship is shown in Equation (8):

[0106]

[0107] Define the components f cx ,f cy of the contact force received when the moving scroll plate contacts the stationary scroll plate in the XY coordinate system, and the components f cn ,f ct in the n-t coordinate system. The relationship is shown in Equation (9):

[0108]

[0109] Ignoring external resistance, the moving scroll plate is only affected by the thrust generated by the linear motor and the contact force after contacting the stationary scroll plate. Therefore, the relationship between the speed and force of the moving scroll plate can be expressed by Equation (10):

[0110]

[0111] In Equation (10), k f is the thrust coefficient of the linear motor; m is the mass of the moving scroll plate, and both are constants.

[0112] Multiply both sides of Equation (10) by the expression of the coordinate transformation matrix as shown in Equation (11):

[0113]

[0114] The derivative of the coordinate transformation matrix involves the derivative of θ with respect to time. The relationships between θ, displacement, and speed are expressed as follows:

[0115]

[0116] After differentiating Equation (7) and combining Equations (11) and (12), the relationships between variables such as displacement, speed, and thrust of the particle in the n-t coordinate system can be obtained.

[0117]

[0118] The relationship between the normal displacement s n and the normal speed v n can be expressed as:

[0119]

[0120] 4.2 Design of the controller

[0121] From Equations (13) and (14), the input-output relationship of the system can be obtained, as Figure 8 shown.

[0122] Figure 8 (a) and Figure 8 The dashed parts in (b) both represent the controlled object. Since the response speed of the current is much faster than that of the mechanical motion, it is considered that the gain of the current controller is constantly 1, so the description of the current controller is omitted.

[0123] Figure 8 The controlled object in (a) is a second-order system. In order to make s n eventually converge, it can be designed as a PD closed-loop controller with as the reference value. The position reference value in the figure is superimposed with the actual position s n (s) to adjust the parameters of the PD closed-loop controller, and the correction of the position quantity is completed through the position closed-loop.

[0124] Figure 8 The controlled object in (b) is a first-order inertia link. In order to make v t eventually reach the expected value, it can be designed as a PI closed-loop controller with as the reference value. The speed reference value in the figure is superimposed with the actual speed v t (s) to adjust the parameters of the PI closed-loop controller, and the correction of the speed quantity is carried out through the speed closed-loop.

[0125] Combine Figure 7 with Figure 8 , and the overall control diagram of the system is as shown in Figure 9 . Figure 9 In, since the normal contact force obtained by coordinate transformation of the value of the force sensor is negative, this value needs to be multiplied by -1 before being fed back to the control system.

[0126] As shown in Figure 10 , a method for controlling the lateral contact force of a direct-drive scroll machine in this embodiment includes the following steps:

[0127] S1. Read the variable information v x , v y , s x , s y , f cx , f cy of the moving scroll in the XY coordinate system after the motor runs, and perform coordinate transformation to map it to the normal-tangential coordinate system, that is, the n-t coordinate system, to obtain the current speed

[0128] v t , the actual position s n , and the current contact force f cn ; where, v x , v y are speed components, s x, s y is the position, f cx , f cy is the thrust force;

[0129] S2. Given a desired normal contact force f dn , which is superimposed with the current contact force f cn to generate a revised amount of the position through an impedance controller

[0130] S3. The revised amount of the position is superimposed with the desired position to generate a reference value of the position

[0131] S4. The reference value of the position is superimposed with the actual position s n to generate a deviation value

[0132] S5. The deviation value obtains the current component i qn through position closed-loop control;

[0133] S6. Given a tangential reference velocity , which is superimposed with the current velocity v t to generate a deviation value

[0134] S7. The deviation value obtains the current component i qt through velocity closed-loop control;

[0135] S8. The current components i qn , i qt in the normal-tangential coordinate system are transformed through coordinate transformation to obtain the current components i qx , i qy in the XY coordinate system;

[0136] S9. According to the current components obtained in step S8, the motor drives the orbiting scroll of the scroll machine to move;

[0137] S10. Determine whether the desired normal contact force f dn is reached. If so, return to step S1; if not, execute step S11;

[0138] S11. Determine whether a fault is caused by the contact force being too large or too small. If not, return to step S1; if so, stop.

[0139] In step S1 of this embodiment, the coordinate system is transformed from the XY coordinate system to the normal-tangential coordinate system, and the specific transformation of the variable information is as follows:

[0140] The projection of the velocity of the moving scroll during its translational motion in the n-t coordinate system has two components, namely the normal and tangential components. Among them, the normal component v of the velocity n >0 indicates that the translational radius increases, and vice versa; the tangential component v of the velocity t >0 indicates that the translation is in the counterclockwise direction, and vice versa, the translation is in the clockwise direction;

[0141] Define the velocity components v of the XY coordinate system x , v y and the velocity components v in the n-t coordinate system n , v t are related as shown in Equation (7):

[0142]

[0143] The thrust force on the moving scroll is generated by the motor, and the thrust is related to the q-axis current of the motor; the q-axis current of the X-axis motor is denoted as i qx , and the q-axis current of the Y-axis motor is denoted as i qy ; Define i qx , i qy and the current components i in the n-t coordinate system qn , i qt are related as shown in Equation (8):

[0144]

[0145] Define the components f of the contact force received when the moving scroll contacts the stationary scroll in the XY coordinates cx , f cy and the components f in the n-t coordinates cn , f ct are related as shown in Equation (9):

[0146]

[0147] The moving scroll is only affected by the thrust force generated by the motor and the contact force after contacting the stationary scroll. Therefore, the relationship between the velocity and force of the moving scroll is expressed by Equation (10):

[0148]

[0149] In Equation (10), k f is the thrust coefficient of the linear motor; m is the mass of the moving scroll, and both are constants;

[0150] Multiply both sides of Equation (10) by the expression of the coordinate transformation matrix as shown in Equation (11):

[0151]

[0152] Derivation of the coordinate transformation matrix involves the derivative of θ with respect to time. The relationships between θ, displacement, and velocity are expressed as follows:

[0153]

[0154] After taking the derivative of Equation (7) and combining with Equations (11) and (12), the relationships between the displacement, velocity, and thrust variables of the particle in the n-t coordinate system are obtained.

[0155]

[0156] The normal displacement s n and the normal velocity v n are related as follows:

[0157]

[0158] In step S2 of this embodiment, the compliant controller generates a revised amount of the position The specific process is as follows: Given a desired normal contact force f dn , which is superimposed with the current contact force f cn . During the contact process between the moving and static scrolls, the contact force may be too large or too small. To achieve effective control of the force, an impedance controller is introduced to correct the deviation of the contact force (based on the difference between the desired normal contact force f dn and the current contact force f cn , which is used as the input of the compliant controller. After the action of the impedance controller, a position correction amount is output. Finally, through the position closed-loop and coordinate transformation in step S5, the current contact force is continuously adjusted to reach the desired contact force magnitude), thereby generating a position correction amount.

[0159] In step S5 of this embodiment, the closed-loop control is as follows: The position reference value is superimposed with the actual position s n to generate a position deviation value. By adjusting the parameters of the PD closed-loop controller (according to the formula M is the desired inertia coefficient, w n affects the stability of the closed-loop control system, ε affects the overshoot of the system, and k p and k d being too large or too small will cause system instability and excessive overshoot. By continuously adjusting the parameters k p and k d , the stability of the system is improved while reducing the overshoot of the system), the output i qn , i qn obtains s n through the integral link, and the position quantity is corrected through the position closed-loop control.

[0160] In step S7 of this embodiment, the closed-loop control is specifically as follows: the speed reference value is superimposed with the actual speed v t to generate a speed deviation value. By adjusting the parameters of the PI closed-loop controller (according to the formula where M is the desired inertia coefficient, w n affects the stability of the closed-loop control system, ε affects the overshoot of the system, k p and k i being too large or too small will cause the system to be unstable and have too large an overshoot. By continuously adjusting the parameters k p and k i to improve the stability of the system and reduce the overshoot of the system), the output is i qt , i qt which passes through an integration link and then outputs v t , and the speed quantity is corrected through the speed closed-loop.

[0161] In step S8 of this embodiment, the current components i qn , i qt in the normal-tangential coordinate system are transformed through coordinate transformation to obtain the current components i qn , i qt in the XY coordinate system. The specific process is as follows: According to the transformation relation formula from the XY coordinate system to the normal-tangential coordinate system and the defined i qx , i qy and the relation formula between the current components i qn , i qt in the n-t coordinate system to achieve the transformation of the current components from the normal-tangential coordinate system to the XY coordinate system.

[0162] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Those skilled in the art can easily think of changes or substitutions within the technical scope disclosed in this application, and all should be covered within the protection scope of this application. Therefore, the scope of this application should be subject to the protection scope of the claims.

Claims

1. A method for controlling the lateral contact force of a direct-drive scroll machine, characterized in that, It includes the following steps: S1. Read the variable information v of the orbiting scroll of the scroll compressor after the motor runs in the XY coordinate system x 、v y 、s x 、s y 、f cx 、f cy ,and perform coordinate transformation to map it to the normal-tangential coordinate system, i.e., the n-t coordinate system, to obtain the current velocity v t 、the actual position s n 、the current contact force f cn ; Among them, v x and v y are velocity components, s x and s y are positions, f cx and f cy are thrusts; S2. Given a desired normal contact force f dn , which is superimposed with the current contact force f cn to generate a revised amount of position through an impedance controller S3. Revised amount of position is superimposed with the desired position to generate a reference value of the position S4. Reference value of position and the actual position s n are subjected to a superposition operation to generate a deviation value S5. Deviation value The current component i is obtained through position closed-loop control qn ; S6. Given a tangential reference speed which is superimposed with the current speed v t to generate a deviation value S7. Deviation value Obtain the current component i through speed closed-loop control qt ; Current components \(i_{n}\) and \(i_{t}\) in the normal-tangential coordinate system qn and \(i_{t}\) qt are transformed through coordinate transformation to obtain current components \(i_{x}\) qx and \(i_{y}\) qy ; S9. According to the current component obtained in step S8, the motor drives the orbiting scroll of the scroll compressor to move; S10. Determine whether the normal expected contact force f is reached dn , if so, return to step S1; if not, execute step S11; S11. Determine whether a fault is caused by excessive or too small contact force. If not, return to step S1; if so, stop.

2. The method for controlling the lateral contact force of a direct-drive scroll machine according to claim 1, characterized in that, In step S1, the transformation from the XY coordinate system to the normal-tangential coordinate system is performed, and the specific transformation of the variable information is as follows: The projection of the velocity during the translational motion of the moving scroll in the n-t coordinate system has two components, namely the normal and tangential components. Among them, the normal component v of the velocity n > 0 indicates that the translational radius increases, and vice versa; the tangential component v of the velocity t > 0 indicates that the translational motion is in the counterclockwise direction, and vice versa, the translational motion is in the clockwise direction; Define the velocity components \(v_x\) and \(v_y\) of the XY coordinate system x , \(v_x\) y and the velocity components \(v_n\) and \(v_t\) in the n-t coordinate system n , \(v_n\) t are related as shown in Equation (7): The thrust received by the moving scroll is generated by the motor, and the thrust is related to the q-axis current of the motor; the q-axis current of the X-axis motor is denoted as i qx , and the q-axis current of the Y-axis motor is denoted as i qy ; Define i qx , i qy and the current components i qn , i qt in the n-t coordinate system are related as shown in Equation (8): Define the components f cx , f cy of the contact force exerted on the moving scroll when it contacts the stationary scroll of the scroll machine in the XY coordinate system, and the components f cn , f ct in the n-t coordinate system. Their relationship is shown in Equation (9): The orbiting scroll is only affected by the thrust generated by the motor and the contact force after contacting the stationary scroll. Therefore, the relationship between the speed and force of the orbiting scroll is expressed by Equation (10): In Equation (10), k f is the thrust coefficient of the linear motor; m is the mass of the moving scroll, and both are constants; Multiply both sides of Equation (10) by the expression of the coordinate transformation matrix as shown in Equation (11): Derivation of the coordinate transformation matrix involves the derivative of θ with respect to time. The relationships between θ, displacement, and velocity are expressed as follows: After differentiating Equation (7) and combining Equations (11) and (12), the relationship between the displacement, speed, and thrust variables of the particle in the n-t coordinate is obtained. Normal displacement s n and normal velocity v n are related as follows:

3. The method for controlling the lateral contact force of a direct-drive scroll machine according to claim 1, characterized in that, In step S2, the impedance controller generates a revised amount of the position The specific process is as follows: A desired normal contact force f dn is given, which is superimposed on the current contact force f cn and the impedance controller is introduced to correct the deviation of the contact force 4. The method for controlling the lateral contact force of a direct-drive scroll machine according to claim 3, characterized in that, In step S2, the impedance controller corrects the deviation of the contact force as follows: according to the difference between the desired normal contact force f dn and the current contact force f cn , which is used as the input of the impedance controller. After the action of the impedance controller, a position correction amount is output.

5. A method for controlling the lateral contact force of a direct drive scroll compressor according to claim 1, characterized in that In step S5, the closed-loop control is as follows: the position reference value is superimposed on the actual position s n to generate a position deviation value By adjusting the parameters of the PD closed-loop controller, the output i qn , i qn obtains s after passing through the integration link n , and the position quantity is corrected through position closed-loop control.

6. A method for controlling the lateral contact force of a direct drive scroll compressor according to claim 5, characterized in that In step S5, the parameters of the PD closed-loop controller are adjusted as follows: According to the formula M is the desired inertia coefficient, w n affects the stability of the closed-loop control system, ε affects the overshoot of the system, and adjust the parameter k p and k d .

7. A method for controlling the lateral contact force of a direct drive scroll compressor according to claim 1, characterized in that In step S7, the closed-loop control is as follows: the speed reference value is superimposed on the actual speed v t to generate a speed deviation value By adjusting the parameters of the PI closed-loop controller, the output is i qt , and i qt passes through an integration link to output v t , and the speed quantity is corrected through the speed closed-loop.

8. A method for controlling the lateral contact force of a direct drive scroll compressor according to claim 7, characterized in that In step S7, the parameters of the PI closed-loop controller are adjusted as follows: According to the formula M is the desired inertia coefficient, w n affects the stability of the closed-loop control system, ε affects the overshoot of the system, and the parameters k p and k i are adjusted.

9. A method for controlling the lateral contact force of a direct drive scroll compressor according to any one of claims 1-8, characterized in that In step S8, the current components i qn and i qt in the normal-tangential coordinate system are transformed to obtain the current components i qn and i qt in the XY coordinate system through coordinate transformation. The specific process is as follows: According to the transformation relation for transforming the XY coordinate system to the normal-tangential coordinate system and the defined i qx , i qy and the relation between the current components i qn and i qt in the n-t coordinate system, the transformation of the current components from the normal-tangential coordinate system to the XY coordinate system is realized.

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