## Dynamic accuracy of Shenzhen Double Ten Instrument

Date：2020/12/14 8:54:01 / Read： / Source：本站

Dynamic accuracy of Shenzhen Double Ten Instrument
In the measurement process, the measured parameter: does not change with time is called static measurement. When the measured parameter changes with time, such as
Surface roughness measurement and gear meshing accuracy measurement are called dynamic measurement.
Dynamic measurement will bring dynamic errors. In order to avoid or reduce the dynamic error, the dynamic characteristics of the instrument must be studied, and the analysis only
The dynamic error of the device under given conditions, and then choose a reasonable dynamic test plan or take targeted improvement measures.
The general method of dynamic error analysis is based on the dynamic equation of the measurement system
Degree index. It not only considers the accuracy of geometric dimensions,
Process and other factors.
, Find out the precision of dynamic accuracy characteristics
Moreover, the inertia, damping, friction of the instrument and the transition of the electrical circuit are also considered.
For contact measurement systems, the main dynamic accuracy indicators are
1.The critical frequency characteristic of the measured change.
2. The critical feeding speed of the tested flea.
3.Limit dynamic side t error.
For the non-contact t measuring system, the main dynamic accuracy index is
1. Error amplitude characteristics.
2. Error transition function. Shenzhen Double Ten dwinauto.com
1. Critical pre-rate characteristics
It determines the relationship between the size change rate and the amplitude at the moment when the transmission pair of the transmission size is disconnected. Transfer size
The moving pair includes parts and probes, as well as all transmission pairs in the measuring chain. The critical frequency is when the transmission pair that transmits the size begins to disengage
The rate of size change.
The general calculation method is as follows:
i. List the motion differential equation of the measurement system or sensor
Where a, b,. Is the constant of the measurement system; z(t) is the system output; f (t) is the system input.
2. Substitute the non-detachment condition f(t)>0 into the equation and find the frequency of size change. Relationship with other parameters.
3. Convert the inequality into an equation to find the critical frequency.
2. The critical feed speed of the piece
The critical speed is the condition for the dynamic error when the size of the contact measuring instrument is suddenly added.
It is determined by the feeding speed of the test piece when it is on.
The calculation step is roughly: Shenzhen Double Ten dwinauto.com
i. Write the differential equation of motion of the measurement system.
2. Calculate the speed of the probe after being impacted when the test piece is fed in,
Critical linear velocity.
Substituting into the non-disengagement conditional formula, the parts can be fed
If the test piece is fed into the measuring position,
The critical speed of falling, within this speed,
The probe is in the raised state and the measurement is carried out when the probe is dropped, then it should be changed to the probe
No system dynamic error occurs after the probe falls.
Three, limit dynamic error
The limit error is given after the transmission pair of the measuring chain is slightly disengaged. The limit value of the dynamic error generated, the general calculation method is:
Prison, precision amplitude-frequency characteristics
It is used to determine the dynamic accuracy of a continuously changing non-contact measurement system, such as non-contact measurement of rotating parts or several
What shape automatic measuring instrument.
The accuracy amplitude-frequency characteristic represents the relationship between the error of the indication amplitude and the angular velocity of the measured change.
AA (w)=month(.)-A,
The general mathematical expression is Shenzhen Double Ten dwinauto.com
In the formula, A(w)—measure the amplitude-frequency characteristics of the system under the condition of a given size change range.
Heart--Measure the static indication range of the system under the given size change range.
The amplitude-frequency characteristics of the measurement system can be obtained by the automatic adjustment principle method.
Studies have shown that, in the case of using precision amplitude-frequency characteristics, the random error of the measurement system can be divided into I'-
(1) Random errors related to the working frequency of the measurement system;
(2) Random errors that have nothing to do with the operating frequency of the measurement system, they have their own frequency.
All interferences related to the frequency of the dimension change of the side being side are the sources of the first type of random error, such as spindle clearance, transmission failure
Homogeneity, unconsidered vibration, and unpredictable shape of the tested part. The frequency of these interferences may be equal to the operating frequency
The rate may also be a multiple of it. Its dispersion is represented by D,,.
All independent interferences belong to the second type of random error sources, such as voltage or air pressure instability, space or external interference
Wait. Its dispersion is represented by D,:.
These two types of random errors are not related to each other, so the total dispersion is equal to D,=D,,+D,z Shenzhen Double Ten dwinauto.com
The random part of the dynamic accuracy characteristics it represents is expressed by the maximum limit error: AA, (w)
Determining the complete expression with the characteristic of precision and amplitude. That is, the complete expression composed of two parts: systematic and random. System error
The difference is the mathematical expectation M[AAr(w)] of the accuracy amplitude-frequency characteristic, that is, the accuracy amplitude-frequency characteristic formula (2-84) without considering the random error
That is to say [AAr(w)]="(.)
So AAr((o)=M[AAr ((o)±3o(w)] (2-86)
From this, the maximum value of the complete expression of the precision amplitude-frequency characteristic can be abbreviated as
AAr(w)=M[AAr(w)]±3v (w) (2-87)
when. =0, there is no dynamic system error, then