Multi-grinding-head rigid finish machining device for screw rotor and synchronous control method

Abstract

The invention discloses a multi-grinding-head rigid finish machining device for a screw rotor and a synchronous control method, and relates to the technical field of precision manufacturing, the multi-grinding-head rigid finish machining device comprises a supporting base and a supporting frame arranged on the supporting base, a plurality of guide mechanisms are arranged in the supporting frame, and each guide mechanism comprises a guide pipe and a connecting rod; one end of the connecting rod is arranged in the guide pipe, the other end of the connecting rod is connected with the servo motor, and the grinding wheel is arranged on the servo motor; the synchronous control method comprises the following steps: collecting a compression force signal of the pressure spring; establishing a material removal depth model; calculating a grinding wheel rotating speed; dynamically adjusting the output rotating speed of the servo motor; a compensation signal is generated, and dynamic synchronous control is conducted on the multiple grinding wheels; along with rotation of the screw rotor, the grinding wheels can move up and down along the outline of the screw rotor under the action of the springs, meanwhile, through dynamic synchronous control over the multiple grinding wheels, the quality and efficiency of fine polishing operation of the screw rotor can be effectively improved, and important application value is achieved.

Description

Technical Field

[0001] The present invention relates to the field of precision manufacturing technology, and in particular to a multi-grinding head rigid finishing device for a screw rotor and a synchronous control method. Background Art

[0002] In the field of oil extraction, screw drill tools are an important downhole power drilling tool and are widely used in oil extraction. As the core component of the drill tool, the screw rotor needs to have very high surface quality and precision, and fine polishing is one of the key processing steps to achieve high surface quality and precision of the screw rotor.

[0003] In the prior art, traditional screw polishing machines often use a sand belt polishing method, which has some obvious shortcomings.

[0004] First, the existing structure is complex, and generally only one end of the screw can be processed at one time. For a multi-head screw, one end needs to be polished before the other ends are polished again. The polishing of the screw needs to be repeated many times to complete.

[0005] Secondly, during the polishing process, the polishing speed of the grinding wheel is fixed and cannot be adjusted in real time according to the contour changes during the processing process, which can easily lead to local over-grinding or under-grinding, affecting the surface consistency.

[0006] Therefore, a multi-grinding head rigid finishing device for a screw rotor and a synchronous control method are provided to solve the above problems. Summary of the Invention

[0007] The purpose of the present invention is to provide a multi-grinding head rigid finishing device and synchronous control method for a screw rotor, which can enable the grinding wheel to adaptively adjust the polishing pressure according to the profile of the screw rotor, and at the same time can control the grinding wheel speed in real time according to the actual pressure changes during the polishing process, thereby ensuring uniform fine polishing operation on the entire screw rotor surface, ensuring the consistency of polishing of different parts of the screw rotor, and solving the problems of low processing efficiency and low processing accuracy of the screw rotor.

[0008] To achieve the above-mentioned purpose, the present invention provides a multi-grinding head rigid finishing device for a screw rotor, comprising a support base and a support frame arranged on the support base, wherein a plurality of guide mechanisms are arranged inside the support frame, and the guide mechanism comprises a guide tube and a connecting rod, wherein one end of the connecting rod is arranged in the guide tube, and the other end of the connecting rod is connected to a servo motor, and a grinding wheel is arranged on the servo motor, and the servo motor and the grinding wheel are connected by a flange.

[0009] Preferably, one end of the connecting rod is set as a rectangular slider, and the other end of the connecting rod is set as a cylinder. A pressure spring is set at the bottom of the rectangular slider, and a pressure sensor is set at the other end of the pressure spring. The rectangular slider, pressure spring and pressure sensor are all set in the square guide hole of the guide tube, and the cylinder passes through the circular guide hole of the guide tube and is connected to the servo motor.

[0010] Preferably, a plurality of grinding wheels are arranged at equal angles along the circumference of the screw rotor, and a pre-pressing amount is provided between the polishing surface of the grinding wheel and the machined surface of the screw rotor, and the pre-pressing amount is set to 0.05 mm-0.15 mm.

[0011] A synchronous control method for a multi-grinding head rigid finishing device for a screw rotor comprises the following steps:

[0012] S1: Collect the compression force signal of the pressure spring through the pressure sensor;

[0013] S2: Establish material removal depth model through Preston equation and Hertz contact theory;

[0014] S3: Calculate the grinding wheel speed based on the compression force signal of the pressure spring;

[0015] S4: Dynamically adjust the output speed of the servo motor according to the grinding wheel speed, and use the speed and current dual closed-loop control strategy to control the servo motor;

[0016] S5: Through the deviation coupling speed compensator, the speed differences of different servo motors are weighted and summed to generate compensation signals, and the dynamic synchronization control of multiple grinding wheels is performed based on the compensation signals.

[0017] Preferably, step S2 specifically includes the following steps:

[0018] S21: The basic framework of the material removal depth model is constructed using the Preston equation. The specific setting of the Preston equation is:

[0019] h=K p P0v r t

[0020] Where h represents the normal material removal depth of the screw rotor, K p Indicates the material removal rate influence coefficient, material removal rate influence coefficient K p The influencing parameters are set as the grinding workpiece material, grinding tool curvature radius, abrasive material and ambient temperature. P0 represents the maximum pressure at the contact point between the grinding wheel and the screw rotor, and v r It represents the relative speed of the contact point between the grinding wheel and the screw rotor, and t represents the polishing time;

[0021] S22: The mechanical properties of the contact surface between the grinding wheel and the screw rotor are constructed using the Hertz contact theory. The specific settings of the Hertz contact theory are:

[0022]

[0023] Wherein, x represents the abscissa of the contact point between the grinding wheel and the screw rotor, y represents the ordinate of the contact point between the grinding wheel and the screw rotor, a represents the major axis of the ellipse in the contact area between the grinding wheel and the screw rotor, and b represents the minor axis of the ellipse in the contact area between the grinding wheel and the screw rotor.

[0024] Preferably, in step S22, the major axis a of the ellipse in the contact area between the grinding wheel and the screw rotor and the minor axis b of the ellipse in the contact area between the grinding wheel and the screw rotor are respectively expressed as:

[0025]

[0026]

[0027] Among them, A represents the relative principal curvature of the grinding wheel at the contact point, B represents the relative principal curvature of the screw rotor at the contact point, and E c represents the relative Young's modulus, k represents the modulus, ε(k) represents the second kind of elliptic integral, F n Indicates the spring pressure of the pressure spring.

[0028] Preferably, step S3 specifically includes the following steps:

[0029] S31: Calculate the pressure P(x, y) at each contact point in the contact area between the grinding wheel and the screw rotor. The pressure P(x, y) at each contact point is specifically set to:

[0030]

[0031] S32: Calculation of the spring pressure F of the pressure spring n , spring pressure F n The specific settings are:

[0032]

[0033] P0=3F n / 2πab;

[0034] S33: Get spring pressure F n With relative speed v r The mathematical relationship between spring pressure F n With relative speed v r The mathematical relationship is specifically set as:

[0035]

[0036] S34: Set the grinding wheel linear speed to the relative speed v r , the new relative velocity v r The specific settings are:

[0037]

[0038] Among them, r represents the radius of the grinding wheel;

[0039] S35: According to the new relative speed v r , get the grinding wheel speed n and spring pressure F n The relationship between the two is used to calculate the grinding wheel speed n, which is specifically set as:

[0040]

[0041] Preferably, step S4 specifically includes the following steps:

[0042] S41: Through i d = 0 control strategy to build the servo motor model, q-axis voltage u q The voltage equation is specifically set as:

[0043]

[0044] Among them, R s represents the stator resistance, i q represents the q-axis current, L q represents the stator inductance, ω e represents the electrical angular velocity, ψ f represents the permanent magnet flux;

[0045] Calculate the electromagnetic torque T of the servo motor e , electromagnetic torque T e The specific settings are:

[0046]

[0047] Among them, p n represents the number of pole pairs;

[0048] The mechanical motion equation of the servo motor is obtained. The mechanical motion equation of the servo motor is specifically set as:

[0049]

[0050] Where J represents the moment of inertia, ω m represents the mechanical angular velocity, B represents the damping coefficient, T L Indicates load torque;

[0051] S42: Ignore the dynamic phase electrical angular velocity ω e and permanent magnet flux ψf , get the new q-axis voltage u q The voltage equation, the new q-axis voltage u q The voltage equation is specifically set as:

[0052]

[0053] For the new q-axis voltage u q Perform Laplace transform on both sides of the voltage equation to obtain the q-axis current transfer function G of the servo motor c (s), q-axis current transfer function G c (s) is specifically set to:

[0054]

[0055] Among them, i q (s) represents the Laplace transform of the q-axis current, u q (s) represents the Laplace transform of the q-axis voltage, and s represents the complex frequency variable;

[0056] S43: Based on the voltage space vector pulse width modulation technology, the inverter is equivalent to the first-order inertia link G SVPWM (s), first-order inertial link G SVPWM (s) is set to:

[0057]

[0058] Among them, T s Indicates the inverter switching cycle;

[0059] Introducing switching delay T d , we get the delay link transfer function G ys (s), delay link transfer function G ys (s) is specifically set to:

[0060]

[0061] S44: The servo motor inner loop is controlled by the PI current controller. The transfer function G of the PI current controller is c_ctrl (s) is set to:

[0062]

[0063] Among them, k cp represents the proportional gain of the current inner loop PI controller, k ci Represents the integral gain of the current inner loop PI controller;

[0064] S45: Current inner loop open loop transfer function G c_open (s) is determined by the transfer function G of the PI current controllerc_ctrl (s), q-axis current transfer function G c (s), first-order inertia link G SVPWM (s) and the delay link transfer function G ys (s) are connected in series, and the current inner loop open loop transfer function G c_open (s) is specifically set to:

[0065]

[0066] Ignore the inverter switching period T s and switching delay T d , the current inner loop open loop transfer function G c_open (s) Perform the first simplification to obtain the first simplified current inner loop open loop transfer function G c_open (s), the first simplified current inner loop open-loop transfer function G c_open (s) is specifically set to:

[0067]

[0068] make The open-loop transfer function of the current inner loop G c_open (s) Perform the second simplification to obtain the second simplified current inner loop open loop transfer function G c_open (s), the second simplified current inner loop open-loop transfer function G c_open (s) is specifically set to:

[0069]

[0070] Get the corresponding current inner loop closed loop transfer function G s_close (s), current inner loop closed loop transfer function G s_close (s) is specifically set to:

[0071]

[0072] The proportional gain k of the current inner loop PI controller is set cp and the current inner loop PI controller integral gain k ci Set to:

[0073]

[0074]

[0075] Among them, ω c Indicates the open-loop cutoff frequency of the current inner loop PI controller;

[0076] S46: Ignore load torque T L, perform Laplace transform on the mechanical motion equation of the servo motor and obtain the transfer function G of the mechanical motion equation s (s):

[0077]

[0078] Among them, ω r (s) represents the Laplace transform of the mechanical angular velocity, T e (s) represents the Laplace transform of electromagnetic torque;

[0079] S47: The servo motor speed outer loop is controlled by the PI controller. The transfer function G of the PI controller is s_ctrl (s) is specifically set to:

[0080]

[0081] Among them, k sp k represents the proportional gain of the PI controller of the speed outer loop, si Indicates the integral gain of the PI controller of the speed outer loop;

[0082] S48: Open-loop transfer function G of the speed outer loop s_open (s) is determined by the transfer function G of the PI controller s_ctrl (s) and the mechanical motion equation transfer function G s (s) in series and considering the torque constant K e The open-loop transfer function of the speed outer loop is G s_open (s) is specifically set to:

[0083]

[0084] make The open-loop transfer function G of the speed outer loop s_open (s) is simplified to obtain the simplified open-loop transfer function G of the velocity outer loop s_open (s), simplified open-loop transfer function of the velocity outer loop G s_open (s) is specifically set to:

[0085]

[0086] Get the corresponding speed outer loop closed loop transfer function G s_close (s), speed outer loop closed loop transfer function G s_close (s) is specifically set to:

[0087]

[0088] Set the proportional gain k of the PI controller of the speed outer loop sp and the PI controller integral gain k of the speed outer loopsi Set to:

[0089]

[0090]

[0091] Among them, ω s Indicates the open-loop cutoff frequency of the speed outer-loop PI controller.

[0092] Preferably, step S5 specifically includes the following steps:

[0093] S51: Calculate the gain K of the deviation coupling speed compensator pq , gain K pq The specific settings are:

[0094]

[0095] Among them, J p Indicates the moment of inertia of the servo motor being controlled, J q Indicates the moment of inertia of the servo motor involved in the difference calculation;

[0096] S52: Calculate the compensation signal e of the deviation coupling speed compensator p , compensation signal e p The specific settings are:

[0097]

[0098] Among them, e p Represents the speed compensation signal of the p-th motor, ω p Indicates the speed of the servo motor being controlled, ω q Indicates the speed of the servo motor involved in the difference calculation, and N indicates the total number of grinding wheels;

[0099] S53: Compensation signal e p Add it to the speed signal given by the system to get the input speed of the servo motor, and couple the speeds of different servo motors.

[0100] Therefore, the present invention adopts the above-mentioned multi-grinding head rigid finishing device and synchronous control method for a screw rotor, which has the following beneficial effects:

[0101] This solution adopts a device design that adaptively adjusts the position of the grinding wheel according to the profile of the screw rotor, a control method that controls the grinding wheel speed in real time according to the spring compression amount, and a multi-grinding head collaborative polishing method. These methods effectively overcome the problems of uneven polishing and low processing efficiency in traditional polishing methods, allowing the surface of the screw rotor to achieve higher smoothness and precision standards, significantly improving the overall polishing quality and ensuring that the screw rotor performs better in application scenarios such as mechanical transmission.

[0102] The method scheme of the present invention is further described in detail below through the drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] Figure 1 This is a structural diagram of a multi-grinding head rigid finishing device for a screw rotor according to the present invention;

[0104] Figure 2 This is a 3D rendering of a multi-grinding head rigid finishing device for a screw rotor according to the present invention;

[0105] Figure 3 This is a structural diagram of the guide tube of the present invention;

[0106] Figure 4 It is a structural diagram of the connecting rod of the present invention;

[0107] Figure 5 This is a flow chart of a synchronous control method of a multi-grinding head rigid finishing device for a screw rotor according to the present invention;

[0108] Figure 6 is a graph of pressure and corresponding rotational speed according to the present invention;

[0109] Figure 7 This is a structural diagram of the servo motor double closed-loop control of the present invention;

[0110] Figure 8 This is a structural diagram of the deviation coupling coordinated control of multiple servo motors of the present invention;

[0111] Figure 9 This is a result diagram of the simulation of synchronous control of multiple servo motors according to the present invention.

[0112] Among them: 1. Support base; 2. Support frame; 3. Guide mechanism; 4. Guide tube; 5. Connecting rod; 6. Servo motor; 7. Grinding wheel; 8. Rectangular slider; 9. Cylinder; 10. Pressure spring; 11. Pressure sensor. DETAILED DESCRIPTION

[0113] The method scheme of the present invention is further described below through the drawings and examples.

[0114] Unless otherwise defined, technical terms or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0115] The words “include” or “comprising” and similar words used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of also including other elements. The orientation or position relationship indicated by the terms “inside”, “outside”, “upper”, “lower”, etc. is based on the orientation or position relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly stipulated and limited, the terms such as “attachment” should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral whole; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0116] Example

[0117] like Figures 1 to 4 As shown, this embodiment provides a multi-grinding head rigid finishing device for a screw rotor, comprising a support base 1 and a support frame 2 arranged on the support base 1, for integrating and fixing various mechanisms to form a processing device body with spatial rigidity.

[0118] A plurality of guide mechanisms 3 are provided inside the support frame 2 . In this embodiment, the number of the guide mechanisms 3 is five.

[0119] The guide mechanism 3 includes a guide tube 4 and a connecting rod 5. One end of the connecting rod 5 is arranged in the guide tube 4, and the other end of the connecting rod 5 is connected to the servo motor 6. A grinding wheel 7 is provided on the servo motor 6. The servo motor 6 and the grinding wheel 7 are connected by a flange. Each servo motor 6 drives the corresponding grinding wheel 7 to rotate around its axis through a flange direct connection.

[0120] One end of the connecting rod 5 is set as a rectangular slider 8, and the other end of the connecting rod 5 is set as a cylinder 9. A pressure spring 10 is set at the bottom of the rectangular slider 8, and a pressure sensor 11 is set at the other end of the pressure spring 10. The preload force of the pressure spring 10 enables the grinding wheel 7 to maintain the initial contact pressure with the surface of the screw rotor. The pressure sensor 11 detects the compression force of the pressure spring 10 in real time. The pressure sensor 11 detects the spring compression force in real time. The spring enables the grinding wheel 7 to adapt to this change, thereby effectively ensuring the uniformity and accuracy of the polishing operation on the entire screw rotor surface, avoiding local excessive or insufficient polishing.

[0121] The rectangular slider 8, pressure spring 10 and pressure sensor 11 are all arranged in the square guide hole of the guide tube 4 to form a sliding pair, which is used to support the servo motor and enable it to move up and down. The cylinder 9 passes through the circular guide hole of the guide tube 4 and is connected to the servo motor 6.

[0122] Multiple grinding wheels 7 are arranged at equal angles along the circumference of the screw rotor. The number of grinding wheels 7 is the same as or different from the number of screw rotor heads. The polishing surface of the grinding wheel 7 and the machined surface of the screw rotor maintain an initial contact pressure configuration, and a pre-pressing amount is set. The pre-pressing amount is set to 0.05mm-0.15mm, aiming to ensure that the surface of the screw rotor meets the required smoothness and precision requirements, thereby ensuring the performance of the screw rotor in subsequent applications.

[0123] like Figures 5 to 9 As shown, a synchronous control method of a multi-grinding head rigid finishing device for a screw rotor includes the following steps:

[0124] S1: The compression force signal of the pressure spring is collected through a pressure sensor, and the sampling frequency of the pressure sensor is greater than 5000Hz;

[0125] S2: Establish a material removal depth model using the Preston equation and Hertz contact theory;

[0126] Step S2 specifically includes the following steps:

[0127] S21: The basic framework of the material removal depth model is constructed using the Preston equation. The specific setting of the Preston equation is:

[0128] h=K p P0v r t

[0129] Where h represents the normal material removal depth of the screw rotor, K p Indicates the material removal rate influence coefficient, material removal rate influence coefficient K p The influencing parameters are set as the grinding workpiece material, grinding tool curvature radius, abrasive material and ambient temperature. P0 represents the maximum pressure at the contact point between the grinding wheel and the screw rotor, and v r It represents the relative speed of the contact point between the grinding wheel and the screw rotor, and t represents the polishing time;

[0130] S22: The mechanical properties of the contact surface between the grinding wheel and the screw rotor are constructed using the Hertz contact theory. The specific settings of the Hertz contact theory are:

[0131]

[0132] Wherein, x represents the abscissa of the contact point between the grinding wheel and the screw rotor, y represents the ordinate of the contact point between the grinding wheel and the screw rotor, a represents the major axis of the ellipse in the contact area between the grinding wheel and the screw rotor, and b represents the minor axis of the ellipse in the contact area between the grinding wheel and the screw rotor.

[0133] In step S22, the major axis a of the ellipse in the contact area between the grinding wheel and the screw rotor and the minor axis b of the ellipse in the contact area between the grinding wheel and the screw rotor are respectively expressed as:

[0134]

[0135]

[0136] Among them, A represents the relative principal curvature of the grinding wheel at the contact point, B represents the relative principal curvature of the screw rotor at the contact point, and E c represents the relative Young's modulus, k represents the modulus, ε(k) represents the second kind of elliptic integral, F n Indicates the spring pressure of the pressure spring.

[0137] S3: Calculate the grinding wheel speed based on the compression force signal of the pressure spring. When the compression force of the pressure spring increases, the grinding wheel speed decreases accordingly. When the compression force of the pressure spring decreases, the grinding wheel speed increases accordingly.

[0138] Step S3 specifically includes the following steps:

[0139] S31: Calculate the pressure P(x, y) at each contact point in the contact area between the grinding wheel and the screw rotor. The pressure P(x, y) at each contact point is specifically set to:

[0140]

[0141] S32: The center of the elliptical contact area bears the greatest pressure. This embodiment takes the maximum removal depth in the contact area as the research object. The normal grinding and polishing force applied to the grinding wheel is borne by the semi-ellipsoid with the elliptical contact area as the bottom surface. The spring pressure F of the pressure spring is calculated. n , spring pressure F n The specific settings are:

[0142]

[0143] P0=3F n / 2πab;

[0144] S33: Get spring pressure F n With relative speed v r The mathematical relationship between spring pressure F n With relative speed v r The mathematical relationship is specifically set as:

[0145]

[0146] S34: Since the screw speed is very low relative to the grinding wheel speed, the grinding wheel linear speed is set to the relative speed v r , the new relative velocity v r The specific settings are:

[0147]

[0148] Among them, r represents the radius of the grinding wheel;

[0149] S35: According to the new relative speed v r , get the grinding wheel speed n and spring pressure F n The relationship between the two is used to calculate the grinding wheel speed n, which is specifically set as:

[0150]

[0151] S4: Dynamically adjust the output speed of the servo motor according to the grinding wheel speed, and use the speed and current dual closed-loop control strategy to control the servo motor;

[0152] Step S4 specifically includes the following steps:

[0153] S41: Through i d = 0 control strategy to build the servo motor model, q-axis voltage u q The voltage equation is specifically set as:

[0154]

[0155] Among them, R s represents the stator resistance, i q represents the q-axis current, L q represents the stator inductance, ω e represents the electrical angular velocity, ψ f represents the permanent magnet flux;

[0156] Calculate the electromagnetic torque T of the servo motor e , electromagnetic torque T e The specific settings are:

[0157]

[0158] Among them, p n represents the number of pole pairs;

[0159] The mechanical motion equation of the servo motor is obtained. The mechanical motion equation of the servo motor is specifically set as:

[0160]

[0161] Where J represents the moment of inertia, ω m represents the mechanical angular velocity, B represents the damping coefficient, T L Indicates load torque;

[0162] S42: Ignore the dynamic phase electrical angular velocity ω e and permanent magnet flux ψ f , get the new q-axis voltage u q The voltage equation, the new q-axis voltage u q The voltage equation is specifically set as:

[0163]

[0164] For the new q-axis voltage u q Perform Laplace transform on both sides of the voltage equation to obtain the q-axis current transfer function G of the servo motor c (s), q-axis current transfer function G c (s) is specifically set to:

[0165]

[0166] Among them, i q (s) represents the Laplace transform of the q-axis current, u q (s) represents the Laplace transform of the q-axis voltage, and s represents the complex frequency variable;

[0167] S43: Based on the voltage space vector pulse width modulation technology, the inverter is equivalent to the first-order inertia link G SVPWM (s), first-order inertial link G SVPWM (s) is set to:

[0168]

[0169] Among them, T s Indicates the inverter switching cycle;

[0170] Introducing switching delay T d , we get the delay link transfer function G ys (s), delay link transfer function G ys (s) is specifically set to:

[0171]

[0172] S44: The servo motor inner loop is controlled by the PI current controller. The transfer function G of the PI current controller is c_ctrl (s) is set to:

[0173]

[0174] Among them, kcp represents the proportional gain of the current inner loop PI controller, k ci Represents the integral gain of the current inner loop PI controller;

[0175] S45: Current inner loop open loop transfer function G c_open (s) is determined by the transfer function G of the PI current controller c_ctrl (s), q-axis current transfer function G c (s), first-order inertia link G SVPWM (s) and the delay link transfer function G ys (s) are connected in series, and the current inner loop open loop transfer function G c_open (s) is specifically set to:

[0176]

[0177] Ignore the inverter switching period T s and switching delay T d , the current inner loop open loop transfer function G c_open (s) Perform the first simplification to obtain the first simplified current inner loop open loop transfer function G c_open (s), the first simplified current inner loop open-loop transfer function G c_open (s) is specifically set to:

[0178]

[0179] make The open-loop transfer function of the current inner loop G c_open (s) Perform the second simplification to obtain the second simplified current inner loop open loop transfer function G c_open (s), the second simplified current inner loop open-loop transfer function G c_open (s) is specifically set to:

[0180]

[0181] Get the corresponding current inner loop closed loop transfer function G s_close (s), current inner loop closed loop transfer function G s_close (s) is specifically set to:

[0182]

[0183] The proportional gain k of the current inner loop PI controller is set cp and the current inner loop PI controller integral gain k ci Set to:

[0184]

[0185]

[0186] Among them, ω c Indicates the open-loop cutoff frequency of the current inner loop PI controller;

[0187] S46: Ignore load torque T L , perform Laplace transform on the mechanical motion equation of the servo motor and obtain the transfer function G of the mechanical motion equation s (s):

[0188]

[0189] Among them, ω r (s) represents the Laplace transform of the mechanical angular velocity, T e (s) represents the Laplace transform of electromagnetic torque;

[0190] S47: The servo motor speed outer loop is controlled by the PI controller. The transfer function G of the PI controller is s_ctrl (s) is specifically set to:

[0191]

[0192] Among them, k sp k represents the proportional gain of the PI controller of the speed outer loop, si Indicates the integral gain of the PI controller of the speed outer loop;

[0193] S48: Open-loop transfer function G of the speed outer loop s_open (s) is determined by the transfer function G of the PI controller s_ctrl (s) and the mechanical motion equation transfer function G s (s) in series and considering the torque constant K e The open-loop transfer function of the speed outer loop is G s_open (s) is specifically set to:

[0194]

[0195] make The open-loop transfer function G of the speed outer loop s_open (s) is simplified to obtain the simplified open-loop transfer function G of the velocity outer loop s_open (s), simplified open-loop transfer function of the velocity outer loop G s_open (s) is specifically set to:

[0196]

[0197] Get the corresponding speed outer loop closed loop transfer function G s_close (s), speed outer loop closed loop transfer function G s_close (s) is specifically set to:

[0198]

[0199] Set the proportional gain k of the PI controller of the speed outer loop sp and the PI controller integral gain k of the speed outer loop si Set to:

[0200]

[0201]

[0202] Among them, ω s Indicates the open-loop cutoff frequency of the speed outer-loop PI controller.

[0203] S5: Through the deviation coupling speed compensator, the speed differences of different servo motors are weighted and summed to generate compensation signals, and the dynamic synchronization control of multiple grinding wheels is performed based on the compensation signals.

[0204] The deviation coupling speed compensator calculates the difference between its own speed and the speed of other motors, then multiplies the difference by the respective speed compensation gain, and then adds the values.

[0205] Step S5 specifically includes the following steps:

[0206] S51: Calculate the gain K of the deviation coupling speed compensator pq , gain K pq The specific settings are:

[0207]

[0208] Among them, J p Indicates the moment of inertia of the servo motor being controlled, J q Indicates the moment of inertia of the servo motor involved in the difference calculation;

[0209] S52: Calculate the compensation signal e of the deviation coupling speed compensator p , compensation signal e p The specific settings are:

[0210]

[0211] Among them, e p Represents the speed compensation signal of the p-th motor, ω p Indicates the speed of the servo motor being controlled, ω q Indicates the speed of the servo motor involved in the difference calculation, and N indicates the total number of grinding wheels;

[0212] The servo motors used in this embodiment are motor 1, motor 2, motor 3, motor 4 and motor 5, and the output results of the speed compensators of motor 1, motor 2, motor 3, motor 4 and motor 5 are respectively set as:

[0213] e1=k 12 (ω1-ω2)+k 13 (ω1-ω3)+k 14 (ω1-ω4)+k 15 (ω1-ω5)

[0214] e2=k 21 (ω2-ω1)+k 23 (ω2-ω3)+k 24 (ω2-ω4)+k 25 (ω2-ω5)

[0215] e3=k 31 (ω3-ω1)+k 32 (ω3-ω2)+k 34 (ω3-ω4)+k 35 (ω3-ω5)

[0216] e4=k 41 (ω4-ω1)+k 42 (ω4-ω2)+k 43 (ω4-ω3)+k 45 (ω4-ω5)

[0217] e5=k 51 (ω5-ω1)+k 52 (ω5-ω2)+k 53 (ω5-ω3)+k 54 (ω5-ω4).

[0218] S53: Compensation signal e p Add it to the speed signal given by the system to get the input speed of the servo motor, and couple the speeds of different servo motors.

[0219] Therefore, the present invention adopts the above-mentioned multi-grinding head rigid finishing device and synchronous control method of the screw rotor, which can enable the grinding wheel to adaptively adjust the polishing pressure according to the profile of the screw rotor, and at the same time can control the grinding wheel speed in real time according to the actual pressure changes during the polishing process, ensuring uniform fine polishing operation on the entire screw rotor surface, ensuring the consistency of polishing different parts of the screw rotor, and solving the problems of low processing efficiency and low processing accuracy of the screw rotor.

[0220] Finally, it should be noted that the above embodiments are only used to illustrate the method scheme of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary method personnel in this field should understand that they can still modify or replace the method scheme of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified method scheme to deviate from the spirit and scope of the method scheme of the present invention.

Claims

1. A multi-grinding head rigid finishing device for a screw rotor, characterized in that: It includes a support base and a support frame arranged on the support base. Multiple guide mechanisms are arranged inside the support frame. The guide mechanism includes a guide tube and a connecting rod. One end of the connecting rod is arranged in the guide tube, and the other end of the connecting rod is connected to the servo motor. A grinding wheel is arranged on the servo motor, and the servo motor and the grinding wheel are connected by a flange.

2. The multi-grinding head rigid finishing device for a screw rotor according to claim 1, characterized in that: One end of the connecting rod is set as a rectangular slider, and the other end of the connecting rod is set as a cylinder. A pressure spring is set at the bottom of the rectangular slider, and a pressure sensor is set at the other end of the pressure spring. The rectangular slider, pressure spring and pressure sensor are all set in the square guide hole of the guide tube, and the cylinder passes through the circular guide hole of the guide tube and is connected to the servo motor.

3. The multi-grinding head rigid finishing device for a screw rotor according to claim 1, characterized in that: Multiple grinding wheels are arranged at equal angles along the circumference of the screw rotor. A pre-pressing amount is set between the polishing surface of the grinding wheel and the processed surface of the screw rotor, and the pre-pressing amount is set to 0.05mm-0.15mm.

4. A synchronous control method for a multi-grinding head rigid finishing device for a screw rotor according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Collect the compression force signal of the pressure spring through the pressure sensor; S2: Establish a material removal depth model using the Preston equation and Hertz contact theory; S3: Calculate the grinding wheel speed based on the compression force signal of the pressure spring; S4: Dynamically adjust the output speed of the servo motor according to the grinding wheel speed, and use the speed and current dual closed-loop control strategy to control the servo motor; S5: Through the deviation coupling speed compensator, the speed differences of different servo motors are weighted and summed to generate compensation signals, and the dynamic synchronization control of multiple grinding wheels is performed based on the compensation signals.

5. The synchronous control method of a multi-grinding head rigid finishing device for a screw rotor according to claim 4, characterized in that: Step S2 specifically includes the following steps: S21: The basic framework of the material removal depth model is constructed using the Preston equation. The specific setting of the Preston equation is: h=K p P0v r t Where h represents the normal material removal depth of the screw rotor, K p Indicates the material removal rate influence coefficient, material removal rate influence coefficient K p The influencing parameters are set as the grinding workpiece material, grinding tool curvature radius, abrasive material and ambient temperature. P0 represents the maximum pressure at the contact point between the grinding wheel and the screw rotor, and v r It represents the relative speed of the contact point between the grinding wheel and the screw rotor, and t represents the polishing time; S22: The mechanical properties of the contact surface between the grinding wheel and the screw rotor are constructed using the Hertz contact theory. The specific settings of the Hertz contact theory are: Wherein, x represents the abscissa of the contact point between the grinding wheel and the screw rotor, y represents the ordinate of the contact point between the grinding wheel and the screw rotor, a represents the major axis of the ellipse in the contact area between the grinding wheel and the screw rotor, and b represents the minor axis of the ellipse in the contact area between the grinding wheel and the screw rotor.

6. The synchronous control method of a multi-grinding head rigid finishing device for a screw rotor according to claim 5, characterized in that: In step S22, the major axis a of the ellipse in the contact area between the grinding wheel and the screw rotor and the minor axis b of the ellipse in the contact area between the grinding wheel and the screw rotor are respectively expressed as: Among them, A represents the relative principal curvature of the grinding wheel at the contact point, B represents the relative principal curvature of the screw rotor at the contact point, and E c represents the relative Young's modulus, k represents the modulus, ε(k) represents the second kind of elliptic integral, F n Indicates the spring pressure of the pressure spring.

7. The synchronous control method of a multi-grinding head rigid finishing device for a screw rotor according to claim 4, characterized in that: Step S3 specifically includes the following steps: S31: Calculate the pressure P(x, y) at each contact point in the contact area between the grinding wheel and the screw rotor. The pressure P(x, y) at each contact point is specifically set to: S32: Calculation of the spring pressure F of the pressure spring n , spring pressure F n The specific settings are: P0=3F n / 2πab; S33: Get spring pressure F n With relative speed v r The mathematical relationship between spring pressure F n With relative speed v r The mathematical relationship is specifically set as: S34: Set the grinding wheel linear speed to the relative speed v r , the new relative velocity v r The specific settings are: Among them, r represents the radius of the grinding wheel; S35: According to the new relative speed v r , get the grinding wheel speed n and spring pressure F n The relationship between the two is used to calculate the grinding wheel speed n, which is specifically set as:

8. The synchronous control method of a multi-grinding head rigid finishing device for a screw rotor according to claim 4, characterized in that: Step S4 specifically includes the following steps: S41: Through i d = 0 control strategy to build the servo motor model, q-axis voltage u q The voltage equation is specifically set as: Among them, R s represents the stator resistance, i q represents the q-axis current, L q represents the stator inductance, ω e represents the electrical angular velocity, ψ f represents the permanent magnet flux; Calculate the electromagnetic torque T of the servo motor e , electromagnetic torque T e The specific settings are: Among them, p n represents the number of pole pairs; The mechanical motion equation of the servo motor is obtained. The mechanical motion equation of the servo motor is specifically set as: Where J represents the moment of inertia, ω m represents the mechanical angular velocity, B represents the damping coefficient, T L Indicates load torque; S42: Ignore the dynamic phase electrical angular velocity ω e and permanent magnet flux ψ f , get the new q-axis voltage u q The voltage equation, the new q-axis voltage u q The voltage equation is specifically set as: For the new q-axis voltage u q Perform Laplace transform on both sides of the voltage equation to obtain the q-axis current transfer function G of the servo motor c (s), q-axis current transfer function G c (s) is specifically set to: Among them, i q (s) represents the Laplace transform of the q-axis current, u q (s) represents the Laplace transform of the q-axis voltage, and s represents the complex frequency variable; S43: Based on the voltage space vector pulse width modulation technology, the inverter is equivalent to the first-order inertia link G SVPWM (s), first-order inertial link G SVPWM (s) is set to: Among them, T s Indicates the inverter switching cycle; Introducing switching delay T d , we get the delay link transfer function G ys (s), delay link transfer function G ys (s) is specifically set to: S44: The servo motor inner loop is controlled by the PI current controller. The transfer function G of the PI current controller is c_ctrl (s) is set to: Among them, k cp represents the proportional gain of the current inner loop PI controller, k ci Represents the integral gain of the current inner loop PI controller; S45: Current inner loop open loop transfer function G c_open (s) is determined by the transfer function G of the PI current controller c_ctrl (s), q-axis current transfer function G c (s), first-order inertia link G SVPWM (s) and the delay link transfer function G ys (s) are connected in series, and the current inner loop open loop transfer function G c_open (s) is specifically set to: Ignore the inverter switching period T s and switching delay T d , the current inner loop open loop transfer function G c_open (s) Perform the first simplification to obtain the first simplified current inner loop open loop transfer function G c_open (s), the first simplified current inner loop open-loop transfer function G c_open (s) is specifically set to: make The open-loop transfer function of the current inner loop G c_open (s) Perform the second simplification to obtain the second simplified current inner loop open loop transfer function G c_open (s), the second simplified current inner loop open-loop transfer function G c_open (s) is specifically set to: Get the corresponding current inner loop closed loop transfer function G s_close (s), current inner loop closed loop transfer function G s_close (s) is specifically set to: The proportional gain k of the current inner loop PI controller is set cp and the current inner loop PI controller integral gain k ci Set to: Among them, ω c Indicates the open-loop cutoff frequency of the current inner loop PI controller; S46: Ignore load torque T L , perform Laplace transform on the mechanical motion equation of the servo motor and obtain the transfer function G of the mechanical motion equation s (s): Among them, ω r (s) represents the Laplace transform of the mechanical angular velocity, T e (s) represents the Laplace transform of electromagnetic torque; S47: The servo motor speed outer loop is controlled by the PI controller. The transfer function G of the PI controller is s_ctrl (s) is specifically set to: Among them, k sp k represents the proportional gain of the PI controller of the speed outer loop, si Indicates the integral gain of the PI controller of the speed outer loop; S48: Open-loop transfer function G of the speed outer loop s_open (s) is determined by the transfer function G of the PI controller s_ctrl (s) and the mechanical motion equation transfer function G s (s) in series and considering the torque constant K e The open-loop transfer function of the speed outer loop is G s_open (s) is specifically set to: make The open-loop transfer function G of the speed outer loop s_open (s) is simplified to obtain the simplified open-loop transfer function G of the velocity outer loop s_open (s), simplified open-loop transfer function of the velocity outer loop G s_open (s) is specifically set to: Get the corresponding speed outer loop closed loop transfer function G s_close (s), speed outer loop closed loop transfer function G s_close (s) is specifically set to: Set the proportional gain k of the PI controller of the speed outer loop sp and the PI controller integral gain k of the speed outer loop si Set to: Among them, ω s Indicates the open-loop cutoff frequency of the speed outer-loop PI controller.

9. The synchronous control method of a multi-grinding head rigid finishing device for a screw rotor according to claim 4, characterized in that: Step S5 specifically includes the following steps: S51: Calculate the gain K of the deviation coupling speed compensator pq , gain K pq The specific settings are: Among them, J p Indicates the moment of inertia of the servo motor being controlled, J q Indicates the moment of inertia of the servo motor involved in the difference calculation; S52: Calculate the compensation signal e of the deviation coupling speed compensator p , compensation signal e p The specific settings are: Among them, e p Represents the speed compensation signal of the p-th motor, ω p Indicates the speed of the servo motor being controlled, ω q Indicates the speed of the servo motor involved in the difference calculation, and N indicates the total number of grinding wheels; S53: Compensation signal e p Add it to the speed signal given by the system to get the input speed of the servo motor, and couple the speeds of different servo motors.

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