563 results about "Dynamic stiffness" patented technology

A method and apparatus is provided for diagnosing and correcting rotating stall and surge in rotating machines by monitoring dynamic shaft precession and comparing this precession with a standard and altering the precession as the machine approaches a destabilizing condition when indicated by the comparison step. Axial vibration monitoring means is also provided for monitoring and comparing a dynamic axial vibration of the machine with a standard and altering the axial vibration as the machine approaches a destabilizing condition. Furthermore, the instant invention measures the complex dynamic stiffness of the machine and computes the direct dynamic stiffness and the quadrature dynamic stiffness for use as a destabilizing warning device by monitoring for a drop in direct dynamic stiffness and / or a coincidence of zero crossing of both the direct dynamic stiffness and the quadrature dynamic stiffness components. One embodiment for altering the rotating stall and / or surge is by a controlled active servobearing.

The invention belongs to the field of polyurethane elastomer synthesis, and particularly relates to a preparation method of a microporous polyurethane elastomer compound with excellent dynamic performance. The compound is characterized in that the compound consists of a polyol mixture component and a modified isocyanate component. The preparation method has the advantages as follows: (1) a quasi-prepolymer method is adopted to process microporous polyurethane elastomer material, the two components has similar viscosity and similar mass mixing ratios, the material mixing temperature is low, the materials are easy to mix evenly, the process control condition is simple, and the operation is easy; and (2) the microporous polyurethane elastomer material prepared by using the compound disclosed by the invention has the advantages that a ratio of dynamic stiffness to static stiffness is smaller than or equal to 1.35, the impact elasticity is larger than or equal to 75 percent, the appearance is not damaged after 3,000,000 times of fatigue tests and the dimensional change rate is smaller than or equal to 20 percent, so that the compound can be used for preparing high-performance products such as damping cushion blocks of high-speed railways and damping elements of automobiles.

Disclosed herein is the structure of a damper that is capable of improving the degree of freedom in design to optimize the damping characteristics of the damper and is capable of allowing the damper to be easily optimized and manufactured for a wide variety of dynamic stiffness characteristics of a tool body, and a manufacturing method using the same. A plurality of ring-shaped elastic members are disposed at opposite ends of a weight part. The weight part is connected to the tool body via the elastic members. Consequently, the weight part is moved relative to the tool body. The plurality of elastic members are mounted while spacers are disposed between the elastic members, and the spacers are moved with respect to the weight part in the axial direction thereof. A viscous fluid is filled in the region surrounded by the outer circumferential surfaces of the spacers, the elastic members, and the inner surface of a hollow part of the tool body. Consequently, it is possible to damp the relative movement of the weight part with respect to the tool body.

The invention discloses a load-bearing adjustable zero-stiffness electromagnetic vibration isolator and a control method thereof. An electromagnetic spring of the vibration isolator in the perpendicular direction is composed of three permanent magnets and two groups of controllable direct current electromagnets, two magnets have opposite polarity and generate repulsive force, and stiffness of theelectromagnetic spring can be adjusted by changing and controlling current. An electromagnetic spring of the vibration isolator in the horizontal direction is composed of two groups of symmetrically distributed electromagnetic springs, and stiffness of the electromagnetic spring can be adjusted by changing and controlling current. When the system load-bearing weight is changed, the stiffness of the perpendicular electromagnetic spring and the stiffness of the horizontal electromagnetic spring are led to meet a certain proportional relationship by adjusting and controlling current so that stiffness of the system at the balance position can be zero. When a vibration isolation device is in small vibration near the balance position, dynamic stiffness is very small, and natural frequency of the whole system is very low so that the vibration isolator can achieve wide-range frequency vibration isolation and has good low frequency vibration isolation effect. In addition, the vibration isolator is compact in structure, light in weight and convenient to control.

The invention discloses a high-speed screw and screw pair comprehensive examination test bed comprising a granite base, a floating guide rail and linear guide rails. The floating guide rail and the linear guide rails are arranged on the granite base parallelly. A linear guide rail holding plate is arranged on the linear guide rails, and the lower side of the linear guide rails is connected with a linear motor arranged on the granite base. A floating guide rail holding plate used for mounting a probe system is arranged on the floating guide rail and is connected with the linear guide rail holding plate through a connecting mechanism. By the aid of the test bed, a function of testing the features such as geometric accuracy, positioning accuracy, backlash, driving speed and acceleration, natural frequency, vibration mode, damping, and static and dynamic stiffness, friction torque and fatigue in the high-speed screw and screw pair and a function of testing stability in the high-speed screw and screw pair can be realized, and the rapid and accurate evaluation on most performance parameters of a precision ball screw can be given.

A quasi-zero stiffness vibration isolator with annular permanent magnets used for generating negative stiffness comprises a base and an outer cylinder connected with the base, the outer permanent magnet is arranged in a top notch of the outer cylinder, an upper cover is connected with the outer cylinder, a sliding bearing is combined with a central hole of the upper cover in a sleeved mode, and a central shaft is sleeved with the sliding bearing and is in clearance fit with the sliding bearing. A sleeve and an adjusting sleeve are sequentially connected to the position, located on the lower portion of the sliding bearing, of the central shaft, and the inner permanent magnet is installed in the sleeve. A spring is arranged at the bottom of the central shaft in a sleeving mode, the bottom end of the spring is fixed to the base, and the top end of the spring is fixed to the adjusting sleeve. A mark line on the central shaft is used for representing the position of the inner permanent magnet relative to the outer permanent magnet. When the mark line coincides with the upper end face of the sliding bearing, the inner permanent magnet exactly faces the outer permanent magnet, and the isolator is in a normal working state. The quasi-zero stiffness vibration isolator has the advantages of being high in static stiffness and low in dynamic stiffness, basic stimulation with large amplitude can be isolated, and the mass of a vibration-isolated objected can be adjusted.

The invention discloses a device for testing dynamic stiffness and constant pressure of a high-speed electric spindle, comprising a base, a loading system, a lubricating and cooling system and an automatic control unit, wherein the loading system comprises a hydraulic cylinder component, a hydraulic cylinder oil way system and a loading rod. In the invention, a loading value and a deformation value are collected through a pressure sensor and a displacement sensor by adopting a hydraulic cylinder and combining the automatic control unit; and the control unit controls the loading pressure of the hydraulic cylinder according to the variation of the loading value and the deformation value and can detect the high-speed electric spindle under the condition of dead load so as to avoid frictional heating generated by mechanical contact in a high-speed running state of the high-speed electric spindle and influence of mechanical wear to test precision and realize continuous and stable dynamic loading and real-time measurement of the high-speed electric spindle, therefore, the invention has high measurement precision and can conveniently finish various functions including data collection, display, storage, analysis, calculation, control, trigger and the like. The whole device has the advantages of compact structure, convenient use and low cost.

A milling head (16) for a milling machine (1) arranged for machining large-size workpieces comprises a fork 18, which is rotatably arranged around a first axis (C) and demonstrates a pair of fork arms (21, 22), which are separated from one another, a spindle device (23), which is arranged between the fork arms and rotatable around a second axis A, a first torque motor (42), which is coupled to the fork 18 for directly driving and controlling of the rotation of the fork around the first axis (C), and a second torque motor (57) for driving and controlling the rotation of the spindle around the second axis (A), said second torque motor being coupled to the spindle device (23) by means of a one-stage toothed gearing (61), which is mechanically clamped free of backlash. The configuration according to the invention is arranged to achieve high torque with high dynamic stiffness and small interference contour of the milling head (16).

The invention belongs to the technical fields of simulating computational analysis and modal testing, and relates to a flutter stability domain modeling approach for a face cutting process. After all kinds of characteristic parameters of a material are known, a computer simulates a machining cutting process, calculates the cutting force in the machining process and analyzes the corresponding cutting coefficient. After the cutting coefficient is obtained, a modal experiment is utilized, modal testing is carried out on a machine tool spindle tool system, and the modal characteristic parameters of the machine tool spindle tool system are analyzed and comprise a multiple-order inherent frequency, a damping ratio, dynamic stiffness and the like. According to a flutter cutting theory, a stability lobe graph is drawn through combining the cutting coefficient and the system characteristic parameters and utilizing a computer assemble program, and is used for selecting the reasonable cutting parameter to avoid a flutter region, the processing precision and quality are improved, and a machine tool system is protected.

The invention relates to a vertical vibration isolation system of single freedom and ultra-low frequency, comprising a mass block, a middle mass block, a zero point generator, a zero stiffness apparatus and a stiffness base. The zero stiffness apparatus invents the dynamic stiffness values of the system at a low cost, which greatly decreases the natural frequency of the system and realizes the passive vibration isolation within the range of ultra-low frequency. The zero point generator reduces the vibration transmissibility in the range of the ultra-low frequency and improves the efficiency of vibration isolation; otherwise, the parameters of the zero point generator can be changed to regulate the system vibration transmissibility according to the actual amplitude and frequency requirements of the vibration isolation. The existing relationship between the zero point generator and the zero stiffness apparatus is: the zero stiffness apparatus decreases the dynamic stiffness value and also brings down the zero value of the zero point generator III and realizes zero within the range of ultra-low frequency.

The invention discloses a test bench of the comprehensive performance of an air spring, and belongs to the technical field of vehicle engineering. The test bench can effectively achieve the aims of carrying out the vertical, transverse and twisting tests of the air spring at the same time and simulating the actual working states of the air spring. A rack of the test bench is in a four stand column type, a bearing platform is arranged in the middle of the rack, a device for bearing balance weight is arranged above the rack, a sensor is arranged below the rack, each stand column of the rack is provided with a cone-shaped fixing nut, a vertical hydraulic actuator which is arranged in a plane triangle mode is arranged below a workbench, and the volume of an additional air chamber is adjustable. The influence to the dynamics performance of the air spring by regional environment with different temperatures can be simulated by an external air conditioner system, multi-dimensional simulation is applied to the air spring through a shock excitation source, changes of loads and deflection of the air spring under the conditions with different environment temperatures and physical parameters are measured, and parameters such as dynamic stiffness, static stiffness, damping ratio and transfer ratio of the air spring are calculated through parameters of vibration characteristics. The test bench is mainly used for testing the comprehensive performance of the air spring.

The invention discloses a comprehensive test device for a linear motor motion system, which belongs to the field of motor test equipment. The comprehensive test device consists of a tested linear motor, a rotating servo motor, a torque motor, a sensor module and a transmission mechanism. Linear motion guide rails and a linear position sensor are fixed on a workbench; a linear motor primary section is arranged on the linear motion guide rails; the output of a controller is connected with each sensor through one communication interface; the sensors transmit position, acceleration, tensile forceand temperature measurement signals obtained in a test process through the communication interfaces; and the rotating servo motor, the torque motor and the linear motor realize coordinated motion with the controller through communication interfaces. The test device can finish the plurality of tests of dynamic stiffness tests, thrust coefficient determination, temperature rise tests, low-speed motion characteristic tests and the like on a linear motor-driven machine tool feeding system, and solve the problems of absence of a complete set of test device, low test accuracy and low repeatability of the linear motor-driven machine tool feeding system.

The invention discloses a method and a device for testing dynamic stiffness of a vibration isolator. The method comprises the steps of establishing an equivalent test model of a single-degree-of-freedom vibration system in a vibration isolation direction by using a static loading device, a combined vibration mass block and an elastic simply supported beam, measuring a frequency response function of the equivalent test model by an exciting method, and then indirectly obtaining the dynamic stiffness of the vibration isolator by virtue of a vibration equation, the similarity of the vibration system and the characteristics of the single-degree-of-freedom system. The method avoids the problem that the existing methods all need to simulate a rated load or a working load with an equivalent mass block in an ingenious way, and solves the problem that the test system is clumsy, high in test cost and test difficulty and even unachievable if the mass block is used for simulating high rated load or working load; the testing device is light and simple in structure, convenient to operate, and economical and practical; the method and the device are applicable to the dynamic stiffness tests of all single-axis vibration isolators, high in applicability, and especially capable of realizing testing of the dynamic stiffness of a large-rated load vibration isolator and ensuring high precision.

The invention provides a method for assessing a technology for a large numerical control machine, comprising the following steps: obtaining frequency response function curve of the large numerical control machine through structure composition dynamic stiffness experiments; employing nonlinear least square method to identify dynamical parameter through curve least square fitting; establishing a non-linear dynamical model of machining process of the numerical control machine by identifying machining technical parameters of cutting force dynamic model in a cutting force experiment; then employing the method of random sampling to simulate tooling motion trail and calculating the number of failpoints to work out probability of technological reliability.With the method of the invention, technological reliability of the numerical control machine can be accurately assessed according to the existing structural characteristics, processing technic characteristics and processing conditions of the large numerical control machine, so that accuracy and high efficiency of technological reliability assessment can be improved and a new method is provided for on-line reliability assessment of the large numerical control machine.

The rail track tie including: a rigid block presenting a bottom face, and a top face for receiving at least one longitudinal rail; a cover for receiving the rigid block and in the form of a rigid shell including a bottom and a peripheral rim around the bottom; and a resilient soleplate disposed between the bottom face of the rigid block and the bottom of the cover. The resilient soleplate has dynamic stiffness k2 lying in the range of 6 kN / mm to 10 kN / mm, and preferably in the range of 6 kN / mm to 8 kN / mm.

The invention relates to a simple precision displacement platform, which comprises a base, a vibration isolator, an internal hexagonal fastening screw, a linear guide rail, an internal hexagonal set screw, a micro-displacement work table, a piezoelectric actuator, a linear grating bar and a linear motor, wherein the displacement platform is a precision one-dimensional displacement platform. As the displacement platform is provided with the linear motor and the piezoelectric actuator, compared with a traditional ball screw mode, the displacement platform has the advantages that intermediate mechanical transmission links are greatly decreased, and the length of a transmission chain is reduced to be zero. The displacement platform is capable of realizing large-displacement rapid positioning and small-displacement precision effective output. Besides, the displacement platform has the advantages of simple structure, high response speed, high precision, high dynamic stiffness, short acceleration and deceleration process, quietness in movement, low noise, high efficiency and the like, and can be used for the field of precision measurement and precision machining.

The invention discloses an active air-floatation support device which comprises an air-floatation support body, an air-film active adjustment unit, a support body detecting unit and a drive control unit, wherein the support body detecting unit measures the state of air-floatation support, the drive control unit generates a control signal according to a detection signal to drive and control the air-film active adjustment unit to generate an active role so as to dynamically adjust the air film form of an air-floatation support surface, thereby dynamically adjusting the pressure distribution of air film gaps of the air-floatation support device, and improving the dynamic stiffness characteristic of air-floatation support. According to the active air-floatation support device, the dynamic stiffness characteristic of air-floatation support can be significantly increased, and the purpose of stabilizing air-floatation support is achieved. In addition, the active air-floatation support device also has the characteristics of compact structure, convenience in control and high precision, thus being especially suitable for occasions of ultra-precision machining or with high-speed spindles with a high requirement on support dynamic stiffness.

An adjustment method for the dynamic stiffness of a rubber joint with liquid damping, and the rubber joint, and the rubber joint comprises metal outer sleeves, a rubber joint body, a throttling channel adjustment device and other parts, wherein the specific structure is as follows: proper holes are arranged on the outer surface of the rubber joint body and pressed-installed with the metal outer sleeves on the outer surfaces thereof to form closed cavities, the cavities are arranged in the relative movement directions of the mandrel and the outer sleeve of the rubber joint body, and symmetrically distributed at the both sides of the axis of the rubber joint body, and the two cavities are connected via a throttling channel; and in this way, when the mandrel and the outer sleeve of the rubber joint perform a relative movement, the volume of one side of each of the cavities at the both sides of the mandrel is reduced, and the volume of the other side is increased, so that a liquid damping medium at the side with the reduced volume flows to the side with the increased volume via pores, and the liquid damping medium generates a damping force while passing through the throttling channel due to damping action. The size of the throttling channel can be changed via the adjustment device, so as to achieve the purposes of adjusting the damping force and obtaining the needed dynamic stiffness.

The invention relates to a system and method for a flutter ground simulation test of an aircraft control surface. The method comprises the steps that random excitation is applied so as to enable a control surface structure (1) to be tested to move; a laser sensor (2) emits X-rays to the control surface structure (1) to be tested, and the local moving speed and the local displacement of the control surface are measured; an aerodynamic force determining device (6) conducts unsteady aerodynamic force calculation according to signals collected by the laser sensor (2), and a loading device (8) is driven to conduct aerodynamic force loading on the control surface structure (1) to be tested. The system and method have the advantages of being simpler, more convenient and easier to do than a conventional air hole test due to the fact that a structure to be test is a real object with proportion of 1:1, maintaining real boundary supporting conditions, being capable of considering dynamic stiffness problem of a steering engine, incapable of bringing additional mass for the system due to the fact that the laser sensor is not in contact with the control surface structure to be tested, greatly simplifying the number and the layout mode of the sensor and shock excitation equipment due to the fact that the aerodynamic force quick calculating system and method are used on the hypothesis of control surface rigidity, and being capable of realizing aerodynamic force calculation in the range of subsonic speed, supersonic velocity and even hypersonic velocity through adjusting an aerodynamic force calculation system and method.

A plane parallel type three-freedom-degree precise positioning work table has three flexible branched chains which are total the same in structure and respectively and correspondingly arranged on the inner sides of three equal sides of a base of a triangular structure and a movable platform arranged on the inner sides of the three flexible branch chains and arranged at the center of the base, wherein the base, the three flexible branched chains and the movable platform are integrally formed, the three flexible branched chains are in flexible connection with the base, displacement input ends of the three flexible branched chains respectively correspond to three included angles of the base, the movable platform is in flexible connection with the three flexible branched chains, a groove is formed between the inner side of each included angle of the base and the corresponding flexible branched chain, a piezoelectric ceramic driver is horizontally arranged in the groove, one end of the piezoelectric ceramic driver is in hertz contact with the displacement input ends of the flexible branched chains, and the other end of the piezoelectric ceramic driver is fixedly connected on the base through bolts. The plane parallel type three-freedom-degree precise positioning work table is compact in structure, flexible to control, high in static and dynamic stiffness, high in kinematic accuracy, low in inertia, free of error accumulation, free of friction and heating and fast in responding.

The invention discloses a negative stiffness adjustable zero stiffness vibration isolation device and an application method thereof, wherein the negative stiffness adjustable zero stiffness vibrationisolation device comprises a bearing table, a positive stiffness mechanism is arranged at the lower side of the bearing table, a plurality of adjustable negative stiffness mechanisms which are centrosymmetrically arranged are connected around the bearing table, the positive stiffness mechanism comprises a vertical elastic element for supporting the bearing table, and the adjustable negative stiffness mechanism comprises a horizontal elastic element for applying horizontal acting force to the bearing table; and the application method comprises the steps of installing a bearing object on the bearing table and then adjusting each height adjusting mechanism to enable the horizontal elastic element to be horizontal. The negative stiffness adjustable zero stiffness vibration isolation device canflexibly adjust the negative stiffness according to the bearing at any time, so that the negative stiffness can be adjusted according to the actual situation after bearing, the negative stiffness adjustable zero stiffness vibration isolation device can be adjusted to ensure that the negative stiffness adjustable zero stiffness vibration isolation device is in an ideal state that the dynamic stiffness is close to zero in a static load state after field installation, the failure of a vibration isolation system can be avoided, and the negative stiffness adjustable zero stiffness vibration isolation device has the advantages of simple structure, easiness in processing, convenience in loading and unloading, reasonable design and easiness in adjustment.

The invention discloses an ultralow frequency vibration isolator based on parallel connection of a positive stiffness spring and a negative stiffness spring, comprising a guide post, a sheath cover, a sliding block, a negative stiffness spring, a lower cover, a guide seat, a ball and a main spring. According to the invention, the main spring (a positive stiffness spring) is connected with the negative stiffness spring in parallel, thus a vibration damper can have the characteristics of high static stiffness and low dynamic stiffness, and zero-hertz ultralow frequency vibration isolation is realized; connection of a screw thread pair is adjusted, thus a stiffness curve of a vibration isolator is adjusted according to vibration isolation quality, and vibration isolation performance can be adjustable; and rolling friction is realized by adopting balls, thus frictional resistance is reduced. The ultralow frequency vibration isolator disclosed by the invention can be used as one component and is applicable to an environment under vibrational excitation, especially an environment under low frequency vibrational excitation, such as a vehicle seat, a suspension, precise instrument vibration isolation as well as vibration attenuation and seismic resistance.

The invention discloses a non-contact detecting system of the running dynamic stiffness of a machine tool spindle, wherein the spindle is arranged on a machine tool. The detecting system comprises a loading device, a force sensor and a displacement detecting device, wherein the loading device comprises a loading platform, at least one electromagnet and a test rod, a first end of the test rod is connected with the spindle, a second end of the test rod is adjacent to the electromagnet, and the electromagnet is powered on to generate electromagnetic force to load the test rod so as to drive the test rod to deflect. The dynamic stiffness of the machine tool acquired through the non-contact detecting system of the running dynamic stiffness of the machine tool spindle is of more practical significance than the dynamic stiffness of the machine tool tested in a static state, dynamic performance of the machine tool is reflected more accurately, acquired stiffness parameters can be used for evaluating the dynamic performance of the machine tool, and the non-contact detecting system is favorable for identifying weak links of the performance of the machine tool and provides a test method for improving the performance of the machine tool.

The invention discloses a torsion quasi-zero stiffness vibration isolator. The torsion quasi-zero stiffness vibration isolator is mainly composed of a negative-stiffness cam-roller-radial spring mechanism and a positive-stiffness rubber spring vulcanized on a first coupling and a second coupling, and is further provided with a radial spring supporting component used for supporting a radial spring and guaranteeing that the radial spring only deforms in the radial direction. When the first coupling and the second coupling rotate relative to each other, the cam-roller-radial spring mechanism generates negative torsion stiffness, the rubber spring has positive torsion stiffness; under the parallel combination of the positive-stiffness element and the negative-stiffness element, the vibration isolator has the high static stiffness and low dynamic stiffness characteristic that the vibration isolator can bear large static loads, namely, the vibration isolator can transmit large static torque. The stiffness is zero at the static balance position, and the micro stiffness characteristic is shown near the static balance position. Thus, the vibration isolator can isolate ultralow-frequency torsion vibration of a shaft system.

The present invention relates to vibration measurement. The dynamic swinging frame rigidity measurement system for large high speed dynamic balance machine includes force hammer, acceleration sensor, charge amplifier and signal analyzer. The force hammer with force sensor is set separately and knocks the bearing seat during measurement, the acceleration sensor is set on the bearing seat, the force sensor and the acceleration sensor have their outputs connected separately to the inputs of charge amplifier, the charge amplifier has its output connected to the input of the signal analyzer. The present invention is simple, easy in operation, fast and reliable, and is suitable for in-situ measurement of harsh environment especially.

The invention aims at providing a three-dimensional vibration isolation device applicable to low-frequency vibration. On a horizontal plane, a decoupling bracket, steel shafts, and an aluminum slide block realizes decoupling of vibration displacement in X and Y directions; a large circular permanent magnet and a small circular permanent magnet serve as negative stiffness elements, and springs serve as positive stiffness elements, thereby forming a low-frequency vibration isolation system of the horizontal plane; in a vertical direction, oblique springs serve as negative stiffness elements due to geometrical characteristics, and a support spring serves as a positive stiffness element to form a low-frequency vibration isolation system in Z direction; and a three-dimensional low-frequency vibration isolation system is formed by combining the two systems. According to the device, the permanent magnets or the springs serve as the negative stiffness elements or positive stiffness elements, lower-frequency vibration isolation is achieved; displacement decoupling in the X, Y and Z directions is achieved; lower dynamic stiffness in the Z direction and an XY plane can be obtained, and a greater carrying capacity can be ensured at the same time; the input energy is not required; and a static balance position can be adjusted to ensure that the vibration occurs near zero stiffness.

The invention relates to a four-axis linkage numerical control machine tool driven by a linear motor, or provides a completely linear-motor-driven four-axis linkage numerical control machine tool that is simple and compact in structure and good in rigidity and can meet the high speed precision processing; the invention consists of a machine bed column, a machine bed base, a worktable arranging seat, an XY worktable module and asymmetrical parallel spindle modules; based on the modular design method, the invention divides the machine tool into two functional modules of the parallel spindle feeding module and the XY worktable module; the four-axis linkage numerical control machine tool driven by the linear motor has the advantages that the whole machine tool is simple and compact in structure, flexible in design, and is also provided with the good structural rigidity and a certain dynamic stiffness. The XY worktable module has the advantages of fast feeding speed, high precision and strong bearing capacity, etc. The two Z-A freedom parallel spindle modules have the advantages of fast feeding speed of a parallel mechanism, high stiffness and strong bearing capacity, meanwhile, the deflection range of the A axis is big, and the maximum deflection angle can reach 90 degrees, thus realizing the vertical-horizontal conversion processing of the spindle.

A milling head (16) for a milling machine (1) arranged for machining large-size workpieces comprises a fork 18, which is rotatably arranged around a first axis (C) and demonstrates a pair of fork arms (21, 22), which are separated from one another, a spindle device (23), which is arranged between the fork arms and rotatable around a second axis A, a first torque motor (42), which is coupled to the fork 18 for directly driving and controlling of the rotation of the fork around the first axis (C), and a second torque motor (57) for driving and controlling the rotation of the spindle around the second axis (A), said second torque motor being coupled to the spindle device (23) by means of a one-stage toothed gearing (61), which is mechanically clamped free of backlash. The configuration according to the invention is arranged to achieve high torque with high dynamic stiffness and small interference contour of the milling head (16).

The invention relates to a method for testing dynamic stiffness of a high-speed main shaft, which is high in testing precision and convenient to operate. The method comprises the radial loading step, the shaft center displacement measuring step and the dynamic stiffness value calculating step, when the radial loading step is performed, a readable loading element is used for pushing a rolling part to be in contact with the tested high-speed main shaft and enabling the direction of loading force to point to the shaft center of the tested high-speed main shaft, and the rolling part performs synchronous autorotation under the action of frictional force during the rotation of the tested high-speed main shaft. A device for testing the dynamic stiffness of the high-speed main shaft, which is simple in structure, small in occupied space, low in cost and high in precision, comprises a radial loading device and a shaft center displacement measuring device, wherein the radial loading device comprises the readable loading element, the rolling part and a fixed frame of the loading element, the loading element is fixed on the fixed frame of the loading element, the rolling part capable of performing the autorotation is assembled at the output end of the loading element, the rolling part is further in contact with the circumferential surface of the tested high-speed main shaft and the direction of the loading force of the loading element points to the shaft center of the tested high-speed main shaft.