阅读说明：本技术 一种电动缸效率测试装置和方法 (Device and method for testing efficiency of electric cylinder ) 是由 童小川 邓攀 夏占 黄强强 陈潇 于 2020-05-22 设计创作，主要内容包括：本发明提出一种电动缸效率测试装置包括控制模块、传感器模块、测试平台；控制模块分别与测试平台和传感器模块连接,用于控制测试平台,并接收传感器模块回传的信号；传感器模块设置在测试平台上,用于采集测试信号；测试平台用于对电动缸进行测试,测试平台包括安装平台、伺服电机、被测电动缸和加载电动缸；安装平台用于支撑伺服电机、被测电动缸和加载电动缸。本发明中测试装置采用智能计算机进行控制,可以实现测试结果的实时输出和显示,操作方式简单快捷,具有很高的人机交互性；同时效率测试装置可以用于测量电动缸产品的全部性能指标,可以实现测试性能的同步完成,减少测试时间,提高测试效率。(The invention provides an electric cylinder efficiency testing device which comprises a control module, a sensor module and a testing platform, wherein the control module is used for controlling the electric cylinder efficiency; the control module is respectively connected with the test platform and the sensor module, and is used for controlling the test platform and receiving a signal returned by the sensor module; the sensor module is arranged on the test platform and used for acquiring test signals; the test platform is used for testing the electric cylinder and comprises an installation platform, a servo motor, a tested electric cylinder and a loading electric cylinder; the mounting platform is used for supporting the servo motor, the tested electric cylinder and the loading electric cylinder. The testing device is controlled by an intelligent computer, so that the real-time output and display of the testing result can be realized, the operation mode is simple and quick, and the human-computer interaction is very high; meanwhile, the efficiency testing device can be used for measuring all performance indexes of the electric cylinder product, the synchronous completion of testing performance can be realized, the testing time is reduced, and the testing efficiency is improved.)

1. The device for testing the efficiency of the electric cylinder is characterized by comprising a control module, a sensor module and a test platform;

the control module is respectively connected with the test platform and the sensor module, and is used for controlling the test platform and receiving the signal returned by the sensor module;

the sensor module is arranged on the test platform and used for acquiring test signals;

the test platform is used for testing the electric cylinder and comprises an installation platform (100), a servo motor (201), a tested electric cylinder (202) and a loading electric cylinder (203);

the mounting platform (100) is used for supporting the servo motor (201), the tested electric cylinder (202) and the loading electric cylinder (203);

the servo motor (201) is connected with the control module and the tested electric cylinder (202) and used for enabling the control module to drive the tested electric cylinder (202) to carry out testing;

the loading electric cylinder (203) is connected with the control module and the tested electric cylinder (202) and is used for providing corresponding reaction force to the tested electric cylinder (202) through driving of the control module.

2. The electric cylinder efficiency testing apparatus according to claim 1, wherein the sensor module includes a torque sensor (301) and a push-pull force sensor (302);

the torque sensor (301) is connected with the output end of the servo motor (201) and is used for collecting the input torque of the electric cylinder efficiency testing device;

the push-pull force sensor (302) is arranged between the tested electric cylinder (202) and the loading electric cylinder (203) and is used for collecting the push-pull force output by the tested electric cylinder (202).

3. The electric cylinder efficiency testing apparatus according to claim 1, wherein the sensor module includes a non-contact displacement sensor and a speed measuring sensor for providing the control module with the push rod movement speed of the tested electric cylinder (202).

4. An electric cylinder efficiency testing method is characterized by comprising the following steps:

step S1: fixing a servo motor (201) and a tested electric cylinder (202) on a test platform and associating each sensor;

step S2: adjusting the piston rod of the tested electric cylinder (202) to an initial position, and controlling the loading electric cylinder (203) to limit torque;

step S3: controlling the tested electric cylinder (202) to move at a constant speed, and acquiring the rotating speed n of the servo motor (201) during the constant speed movement of the tested electric cylinder (202) by the sensors₁And an actual torque output value T and an actual force output value F and speed V of the measured cylinder (202);

step S4: and calculating the efficiency of the tested electric cylinder (202) by the data collected by the sensors, and outputting a calculation result.

5. The electric cylinder efficiency testing method according to claim 1, wherein in step S1, the sensors include a torque sensor (301) and a push-pull force sensor (302);

the torque sensor (301) is connected with the output end of the servo motor (201) and is used for collecting the input torque of the electric cylinder efficiency testing device;

the push-pull force sensor (302) is arranged between the tested electric cylinder (202) and the loading electric cylinder (203) and is used for collecting the push-pull force output by the tested electric cylinder (202).

6. The electric cylinder efficiency testing method according to claim 1, wherein in step S3, the movement speed planning curve of the tested electric cylinder (202) is divided into three phases;

the first stage is an acceleration stage, and the tested electric cylinder (202) is accelerated to a speed V from a static state;

the second stage is a constant speed stage, and the tested electric cylinder (202) performs constant speed motion at the speed V;

the third phase is a deceleration phase, and the tested electric cylinder (202) is decelerated to be static from the speed V.

7. The electric cylinder efficiency testing method according to claim 1, wherein in step S4, the electric cylinder efficiency testing model is:

wherein η represents the transmission efficiency of the electric cylinder, T represents the input torque, n₁Representing the rotational speed of the motor output; v represents the motion speed of the pusher bar assembly; f represents the actual force output value.

Technical Field

The invention relates to the field of electric cylinder performance detection, in particular to an electric cylinder efficiency testing device and method.

Background

With the rapid development and progress of modern industries and equipment manufacturing industries, people have increasingly high requirements on the performance and functions of the execution terminal of the driving process control device under the push and influence of digital technology, micro-processing technology and the like. The traditional hydraulic and pneumatic actuating mechanisms have the characteristics of poor position controllability, inconvenient maintenance, complex system structure, poor sensitivity, high environmental sensitivity, larger leakage, noise pollution and the like, and are difficult to adapt to the requirements of the current industrial development. With the high-speed development of electronic technology, the problems of restricting the speed regulation control and power density of electric drive are gradually solved, and electric drive also becomes a new great trend in the current drive technology field.

An electric cylinder, which is one of the linear electric actuators, is a power base member that has been developed gradually with the development of modern industries. The linear actuator is an integrated high-performance linear actuator, can convert the rotary motion of a motor into linear motion, and can realize accurate force, position and speed control. Due to the excellent performance and reliable quality, the material has been gradually applied to various fields such as industry, national defense and the like, and has a very fast growth speed and very good market prospect. The electric cylinder device mainly comprises a driving unit, a transmission unit, a supporting unit, a guiding unit and an execution unit. Under the drive of the servo motor, the power is transmitted to a driven machine (lead screw) at a fixed reduction ratio through a reduction mechanism such as a synchronous belt/a belt wheel, and the rotary power of the motor is converted into the linear power of the nut through the power conversion action of the lead screw. The efficiency of the electric cylinder is a reflection of the comprehensive performance of the electric cylinder, and can also reflect the power loss inside the electric cylinder. Efficient mechanical actuation has been a pursued goal of engineers. In the actual design and manufacturing process, the accurate measurement of the efficiency of the electric cylinder is the basis for improving the efficiency of the electric cylinder.

Because the electric cylinder is a linear actuating element driven by a pure mechanical structure, the efficiency of the total mechanism of the electric cylinder is directly influenced by factors such as the material and the structure of each mechanism, a plurality of researches aiming at single parts in the electric cylinder are currently carried out at home and abroad, the research related to the efficiency of the electric cylinder is relatively lacked, and products specially used for testing the efficiency of the electric cylinder in the current market are rare.

A PC-processing-based electric cylinder efficiency test platform is designed in 'parallel type multi-level screw electric cylinder transmission efficiency influence factor and structure optimization research' of Master academic thesis of Zhongnan forestry science and technology university, electric cylinders to be tested are loaded through hydraulic cylinders, and real-time monitoring data of sensors are obtained through real-time communication between the PC and a controller. However, when the tested cylinder is loaded by the hydraulic cylinder, the pressure of the hydraulic cylinder cannot be stabilized at the set load in the dynamic process in the contraction phase of the hydraulic cylinder. The unstable change of the loading load can cause the parameters of voltage, current, load and the like to be tested to have larger fluctuation in the measuring process. The pressure of the hydraulic cylinder needs to be adjusted for many times in the test process, the adjustment process is complicated, and the loading mode of the test platform for loading the tested electric cylinder through the hydraulic cylinder needs to be further improved.

Disclosure of Invention

The invention provides an electric cylinder efficiency testing device and method which can overcome the defects that the existing testing device is complicated in testing process by adopting a hydraulic loading device and low in testing efficiency, and can conveniently measure the efficiency of the whole electric cylinder.

The invention particularly provides an electric cylinder efficiency testing device which is characterized by comprising a control module, a sensor module and a testing platform, wherein the control module is used for controlling the electric cylinder efficiency testing device to work;

the control module is respectively connected with the test platform and the sensor module, and is used for controlling the test platform and receiving the signal returned by the sensor module;

the sensor module is arranged on the test platform and used for acquiring test signals;

the test platform is used for testing the electric cylinder and comprises an installation platform, a servo motor, a tested electric cylinder and a loading electric cylinder;

the mounting platform is used for supporting the servo motor, the tested electric cylinder and the loading electric cylinder;

the servo motor is connected with the control module and the tested electric cylinder and is used for enabling the control module to drive the tested electric cylinder to test;

the loading electric cylinder is connected with the control module and the tested electric cylinder and is used for providing corresponding reaction force for the tested electric cylinder through the driving of the control module.

Further, the sensor module comprises a torque sensor and a push-pull force sensor;

the torque sensor is connected with the output end of the servo motor and used for collecting the input torque of the electric cylinder efficiency testing device;

the push-pull force sensor is arranged between the tested electric cylinder and the loading electric cylinder and used for collecting the push-pull force output by the tested electric cylinder.

Still further, the sensor module comprises a non-contact displacement sensor and a speed measurement sensor, and the non-contact displacement sensor and the speed measurement sensor are used for providing the push rod movement speed of the tested electric cylinder for the control module.

The method for testing the efficiency of the electric cylinder is characterized by comprising the following steps:

step S1: fixing the servo motor and the tested electric cylinder on a test platform and associating each sensor;

step S2: adjusting the piston rod of the tested electric cylinder to an initial position, and controlling the loaded electric cylinder to limit the torque;

step S3: controlling the tested electric cylinder to move at a constant speed, and acquiring the rotating speed n of the servo motor during the constant speed movement of the tested electric cylinder by the sensors₁The actual torque output value T, the actual force output value F and the speed V of the tested electric cylinder are obtained;

step S4: and calculating the efficiency of the tested electric cylinder by the data acquired by the sensors, and outputting a calculation result.

Further, in step S1, the sensors include a torque sensor and a push-pull force sensor;

the torque sensor is connected with the output end of the servo motor and used for collecting the input torque of the electric cylinder efficiency testing device;

the push-pull force sensor is arranged between the tested electric cylinder and the loading electric cylinder and used for collecting the push-pull force output by the tested electric cylinder.

Further, in step S3, the measured moving speed planning curve of the cylinder is divided into three phases;

the first stage is an acceleration stage, wherein the tested electric cylinder is accelerated to a speed V from a static state;

the second stage is a constant speed stage, and the tested electric cylinder performs constant speed motion at the speed V;

the third phase is a deceleration phase, and the tested electric cylinder is decelerated to be static from the speed V.

Further, in step S4, the electric cylinder efficiency test model is:

wherein η represents the transmission efficiency of the electric cylinder, T represents the input torque, n₁Representing the rotational speed of the motor output; v represents the motion speed of the pusher bar assembly; f represents the actual force output value.

The invention has the beneficial effects that:

compared with the prior art, the testing device disclosed by the invention is controlled by adopting an intelligent computer, can realize real-time output and display of the testing result, is simple and quick in operation mode and has very high man-machine interaction.

The efficiency testing device can be almost used for measuring all performance indexes of the electric cylinder product, can realize synchronous completion of testing performance, reduces testing time and improves testing efficiency.

The testing device of the invention uses the reinforcing plate to improve the application range of the whole testing platform, belongs to a modular design means, and can realize the efficiency testing of different models of electric cylinder products by simply replacing the testing or modifying specific parts.

Drawings

Fig. 1 is a schematic structural view of a test platform in an electric cylinder efficiency test device provided in an embodiment of the present invention;

fig. 2 is a schematic structural diagram of an electric cylinder efficiency testing device provided in an embodiment of the present invention;

fig. 3 is a schematic flow chart of an electric cylinder efficiency testing method provided by an embodiment of the invention;

FIG. 4 is a schematic diagram of a velocity profile of a tested electric cylinder in a method for testing efficiency of an electric cylinder according to an embodiment of the present invention;

fig. 5 is a schematic diagram illustrating the principle of the efficiency test of the tested electric cylinder in the method for testing the efficiency of the electric cylinder according to the embodiment of the present invention.

The method comprises the following steps of 100-mounting a platform, 101-a servo motor reinforcing plate, 102-a middle reinforcing plate, 103-a loading electric cylinder reinforcing plate, 201-a servo motor, 202-a tested electric cylinder, 203-a loading electric cylinder, 301-a torque sensor and 302-a push-pull force sensor.

Detailed Description

The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings 1-5.

The invention provides an efficiency testing device for an electric cylinder.

The control module is respectively connected with the test platform, the sensor module and the output module and is used for controlling the test platform and the output module and receiving signals returned by the sensor module. In one embodiment, the control module comprises an industrial personal computer, a loading electric cylinder servo control box and a tested electric cylinder servo control box; the industrial personal computer is connected with the loading electric cylinder servo control box, the tested electric cylinder servo control box, the sensor module and the output module respectively by adopting a computer or an FPGA chip, and is used for controlling the loading electric cylinder servo control box, the tested electric cylinder servo control box and the output module and receiving signals returned by the sensor module; the loading electric cylinder servo control box is connected with the test platform and is used for controlling the loading electric cylinder in the test platform; and the servo control box of the tested electric cylinder is connected with the test platform and used for controlling the tested electric cylinder in the test platform.

As shown in fig. 1, the test platform includes a mounting platform 100, a servo motor 201, a tested electric cylinder 202 and a loading electric cylinder 203. The loading electric cylinder 203 and the servo motor 201 are both connected with the control module; the servo motor 201 is controlled by the control module to perform specific motion, so as to drive the tested electric cylinder 202 to move; the loading electric cylinder 203 is controlled by the control module to provide corresponding reaction force.

The sensor module comprises a torque sensor 301, a push-pull force sensor 302, a non-contact displacement sensor, a speed measuring sensor, a temperature sensor, a noise sensor, a laser ranging sensor and the like, wherein each sensor is arranged in the test platform and connected with the control module, and is used for collecting various data of the tested electric cylinder 202 and sending the collected data to the control module.

The output module is connected with the control module and used for outputting the test result of the electric cylinder. In one embodiment, the output module comprises a memory, a display and a printer, and realizes the display, storage and printing of the relevant system test parameter data and the test curve.

The mounting platform 100 comprises a T-slot table for mounting the loading electric cylinder 203, the servo motor 201, the measured electric cylinder 202 and the sensor module. In order to reduce the finish machining area and ensure that the loading electric cylinder 203, the servo motor 201 and the tested electric cylinder 202 can be stably and firmly installed on the T-shaped groove workbench, all devices on the installation platform 100 are installed and fixed on the T-shaped groove workbench through the reinforcing flat plate. The top of the reinforcing flat plate is a mounting plane, and the bottom of the reinforcing flat plate is provided with a T-shaped groove sliding block for fixing with a T-shaped groove workbench.

The reinforcing plate comprises a servo motor reinforcing plate 101, a middle reinforcing plate 102 and a loading electric cylinder reinforcing plate 103, the servo motor reinforcing plate 101, the middle reinforcing plate 102 and the loading electric cylinder reinforcing plate 103 are respectively fixed at the left end, the middle and the right end of the T-shaped groove workbench, positions among the reinforcing plates can be adjusted according to the sizes of the tested electric cylinder 202 and the loading electric cylinder 203, and then the tested electric cylinders 202 of various different models are tested in the testing device. The servo motor 201 and the tested cylinder 202 are parallel to each other and are fixed on the top of the servo motor reinforcing plate 101 in a staggered manner. The servo motor 201 is fixed in front of the left end of the tested electric cylinder 202 through a motor base, and the motor base of the servo motor 201 is fixed on the servo motor reinforcing plate 101 through screws. The output end of the servo motor 201 is connected with the driving pulley and the torque sensor 301 through a coupler. In one embodiment, the coupler is composed of a left half coupler and a right half coupler, the output end of the servo motor 201 is connected with the left half coupler, and the torque sensor 301 is connected with the right half coupler; the two half couplings are connected by bolts through 4 pieces of hexagonal head reamed holes; the torque sensor 301 is provided on a motor base of the servo motor 201.

The cylinder body center shaft of the tested electric cylinder 202 is arranged along the left and right center shaft directions of the T-shaped groove workbench, the left end and the right end of the cylinder body of the tested electric cylinder 202 are respectively connected with the servo motor reinforcing plate 101 and the middle reinforcing plate 102 through supporting seats, the left side of the cylinder body is fixed on the servo motor reinforcing plate 101 through a left tested supporting seat, and the right side of the cylinder body is fixed on the middle reinforcing plate 102 through a right tested supporting seat. In one embodiment, the left measured supporting seat is connected with the cylinder body through a trunnion connecting screw hole on the cylinder body and is fixed on the servo reinforcing plate through a screw; the right measured support base is connected with the cylinder body through a trunnion on the cylinder body and is fixed on the middle reinforcing plate 102 through screws.

The loading electric cylinder 203 and the tested electric cylinder 202 are arranged along the same central axis, the left end and the right end of the cylinder body of the loading electric cylinder 203 are respectively connected with the middle reinforcing plate 102 and the loading electric cylinder reinforcing plate 103 through supporting seats, the left side of the cylinder body of the loading electric cylinder 203 is fixed on the middle reinforcing plate 102 through a left loading supporting seat, and the right side of the cylinder body is fixed on the loading electric cylinder reinforcing plate 103 through a right loading supporting seat. In one embodiment, the left loading support base is connected with the cylinder body through a trunnion connection screw hole on the cylinder body and is fixed on the middle reinforcing plate 102 through a screw; the right loading support seat is connected with the cylinder body through a trunnion on the cylinder body and is fixed on the loading electric cylinder reinforcing plate 103 through a screw.

The middle parts of the tested electric cylinder 202 and the loading electric cylinder 203 are respectively connected with the left end and the right end of the push-pull force sensor 302 through transition sleeves and rigid couplings, and the two half couplings are connected through bolts and nuts. In one embodiment, in order to ensure the coaxiality of the loading electric cylinder 203 and the tested electric cylinder 202, the supporting seats of the loading electric cylinder 203 and the tested electric cylinder 202 are connected with the reinforcing plate through adjusting screws for adjusting the horizontal direction, and the adjusting screws are fixed with the reinforcing plate through screw seats.

As shown in fig. 2, in an embodiment, an industrial personal computer in the control module sets an action behavior of the measured cylinder 202, and outputs an action data signal to a servo control box of the measured cylinder, and the servo control box of the measured cylinder 202 drives a servo motor 201 to perform a specific motion, thereby driving the motion of the measured cylinder 202.

For example, the electric cylinder efficiency testing device carries out electric cylinder efficiency testing, and the industrial personal computer sets corresponding testing parameters to control the work of the tested electric cylinder servo control box and the loading electric cylinder servo control box. When the tested electric cylinder 202 provides pushing force and movement outwards, the loading electric cylinder 203 provides corresponding reaction force, and the push rod loading the electric cylinder 203 contracts or extends along with the movement direction of the tested electric cylinder 202. At this time, the torque sensor 301 and the push-pull force sensor 302 respectively provide the input torque and the output push-pull force of the testing device, and the non-contact displacement sensor and the speed measurement sensor provide the movement speed of the push rod. The data measured by the sensor is transmitted to the industrial personal computer through a data line, the input power and the output power of the tested electric cylinder 202 are generated through data processing by the testing device, and then the efficiency of the electric cylinder is calculated.

The efficiency testing device of the electric cylinder can also test the maximum static load of the electric cylinder, and the piston rod of the tested electric cylinder 202 extends to about 100 mm. The servo motor 201 loading the electric cylinder 203 is locked by braking and remains still in the whole static push and pull test process. And selecting a driving control mode as a force control mode on the servo control box of the tested electric cylinder. Under the two force output states of pushing force and pulling force, the force output of the tested electric cylinder 202 is gradually increased, namely 30kN, 60kN and 90 kN. Observing whether the servo motor 201 has abnormality (such as noise and heating abnormality) under different force outputs, whether each mechanical part of the tested electric cylinder 202 has cracks or plastic deformation, and reading motor current under each force output and an actual force output value fed back by the push-pull force sensor 302.

As shown in fig. 3, the present invention further provides a method for testing efficiency of an electric cylinder, comprising the following steps:

step S1: fixing the servo motor 201 and the tested electric cylinder 202 on a test platform and associating each sensor;

step S2: adjusting the piston rod of the tested electric cylinder 202 to an initial position, and controlling the loading electric cylinder 203 to limit the torque;

step S3: controlling the tested electric cylinder 202 to move at a constant speed, and acquiring the rotating speed n of the servo motor 201 during the constant speed movement of the electric cylinder by each sensor₁And the actual torque output value T and the actual force output value F and speed V of the tested cylinder 202;

step S4: the efficiency of the measured cylinder 202 is calculated from the data collected by the sensors, and the calculation result is output.

Specifically, in step S1, the servo motor 201 and the measured cylinder 202 are fixed to the test platform, and a dynamic torque sensor is additionally provided between the servo motor 201 and the measured cylinder 202 through a tool. The coaxiality of the tested electric cylinder 202 and the loading electric cylinder 203 is adjusted to enable the actuating rods thereof to be on the same axis. A push-pull force sensor is arranged at the connecting part of the tested electric cylinder 202 and the loading electric cylinder 203. The laser speed measuring sensor is adjusted and arranged, and the identification mark of the laser speed measuring sensor is arranged on the push rod of the tested electric cylinder 202.

In step S2, the actuation rod of the measured cylinder 202 is adjusted to the 0mm mark. The loading electric cylinder 203 is set to be in a force control mode through a control module in the electric cylinder efficiency testing device, torque limitation is carried out according to testing requirements, and the corresponding piston rod end output forces are 20kN, 50kN and 80kN, so that the loading electric cylinder 203 has a torque limitation effect similar to damping.

As shown in FIG. 4, in step S3, the tested electric cylinder 202 is set on the control module as a position control mode, taking a position command of 0-600mm as an example, and the tested electricity is tested in the position control processThe movement speed planning curve of the moving cylinder 202 is divided into three stages, the first stage is an acceleration stage, and when the measured moving cylinder 202 runs from 0mm to 100mm, the measured moving cylinder 202 is accelerated from static to speed V; the second stage is a constant speed stage, and the tested electric cylinder 202 runs from 100mm to 500mm at a speed V; the third phase is a deceleration phase, when the electric cylinder runs from 500mm to 600mm position, the tested electric cylinder 202 is decelerated from a speed V to be stationary, and the speed V can take different testing speeds. The control module records the rotating speed n of the servo motor 201 during the uniform motion in the second stage₁The actual torque output value T fed back by the torque sensor, the actual force output value F of the tested electric cylinder 202 fed back by the push-pull force sensor and the speed V fed back by the laser speed measuring sensor.

As shown in fig. 5, in step S4, the servo motor 201 and the measured cylinder 202 mainly include a motor, a speed reducer, a screw nut, and a push rod assembly, and the motor outputs a certain torque and a certain rotation speed, and the torque and the rotation speed are converted into a linear motion of the push rod assembly through a mechanical structure of the screw nut. According to the efficiency test formula:

wherein η represents the transmission efficiency of the electric cylinder; t represents the input torque; ω represents the input rotational angular velocity; v represents the motion speed of the pusher bar assembly; f represents the actual force output value.

Further, the input speed of the motor can be obtained by the control module under the general condition, and the efficiency test formula can be converted into:

wherein n is₁Representing the rotational speed of the motor output.

In general, there is no speed loss in the mechanical transmission, and the efficiency calculation formula can be simplified as follows:

wherein n is₂Representing the rotating speed after passing through the speed reducer; i represents a reduction ratio of the reduction gear; s denotes the lead of the lead screw nut.

Therefore, the rotation speed n of the servo motor 201 during the uniform motion of the electric cylinder acquired by each sensor₁The actual torque output value T fed back by the torque sensor, the actual force output value F of the tested electric cylinder 202 fed back by the push-pull force sensor and the speed V fed back by the laser speed measuring sensor can calculate the transmission efficiency η of the electric cylinder and output the calculated transmission efficiency η.

Although the present invention has been described in terms of the preferred embodiment, it is not intended that the invention be limited to the embodiment. Any equivalent changes or modifications made without departing from the spirit and scope of the present invention also belong to the protection scope of the present invention. The scope of the invention should therefore be determined with reference to the appended claims.