A mechanical arm measuring three degrees of freedom: measuring the three degrees of freedom of the arm, measuring the translation of the object along the X, Y and Z axes, and only measuring and tracking the position and moving parts.
The joint measuring arm is measured by the sensor installed in each joint, thus indirectly measuring the position of the end effector.
So this problem belongs to the robot kinematics forward problem.
Keywords: measurement; Degree of freedom; Posture; Parallel machine tool; Sensor; Signal; Accuracy 1
With the rapid development of application examples, the performance requirements of machines are compared.
Tall man. Traditionally, this machine uses a series of nested stacks, which is bloated due to a series of errors.
The accumulation of chains is not conducive to improving accuracy, and the traditional four-coordinate addition
Narrow processing machine technology, it is also difficult to achieve any additional surface treatment, and
5-axis machining tools are very expensive and slow. Therefore, the structure
High rigidity, high bearing ratio, high positioning accuracy, compact structure, on-line
It attracted the attention of the scholar machine, and the parallel plane was born.
It is recommended to use additional real-time measurement of motion.
Direct measurement mechanism of platform positioning accuracy. The basic idea is to measure the movement of the mobile platform based on the extra measured body movement between the fixed platform and the platform, and by measuring the movement of the mobile platform while driving.
The generated motion characteristics are modeled by pharmacokinetics. Transport sensor device/>; The position of the display solution obtained by the mobile platform. Measurement time
To solve the front-end speed and meet the requirements of real-time control, you can
The benefits are fed back to the precision compensation and control of machine tools in real time.
Based on the above ideas, the position measurement system of parallel machine tool is established.
Errors such as cutting force and joint gap deformation of the machine tool are eliminated, and the positioning accuracy is improved.
Machine. Used for three-degree-of-freedom series mechanism.
The vice rotates very flexibly. People who use mobile vises often need exercise, especially those near the base.
The measuring instrument consists of a series of three-degree-of-freedom mechanisms, which measure different angles by fine-tuning the movable joints of each circle of the cipher board. Its tail end piece is connected with the robot actuator through the interface element.
. When the measuring position of the moving platform of the machine tool changes, the measuring instrument
The movement of the end of the thin plate and the movement of the platform lead to the closure of rice.
By inserting the calculation card into the computer processing software, the relative of each part of the angle between two adjacent rods is measured from the refined password.
Turn signal, by running
The real-time display of the forward kinematics solution shows the current position of the moving parts in the test program.
Measure each board to achieve position measurement.
2
Accuracy analysis mainly affects the body parts of mechanical robots and the installation errors of the Ministry of Education.
Part manufacturing error, machine assembly error and robot accuracy.
In addition, the temperature, the operating force generated to drive the lever action
Resulting in transmission error, control system error, etc. Measure and compensate these errors.
But it is essential in practice.
2. 1 Basic concepts of testing
Any error in the testing process, no matter how perfect the square is.
How to test accurately? Test methods and equipment will inevitably produce tests.
Error, the test results can not be absolutely accurate. Therefore, in order to measure and get the corresponding accuracy.
Test results,
It is necessary to correctly estimate the measurement error and the reliability of the test results.
The test error is the difference between the measured value and the real value, that is
△X = X-X0
Formula: △x- defines the test error;
X-measured value;
X0-true value.
The real value of the measured real size itself.
2.2 Basic types of test errors
1) Wrong division of mathematical expressions-
Relative absolute error and error; -Tools
2) source error division and error error
Difference method, according to the error classification-system error, gradient.
Error, random error and gross error method
3);
4) Conditional division-basic error and additional error;
5) Divide by the measured speed error-static and dynamic error.
Pity. Error error
2.3 indirect measurement/> direct measurement error in the process of indirect measurement
Based on lines. Physical quantities cannot be measured directly, but must be calculated by a certain amount of energy.
The number of direct measurements to determine. Due to direct measurement
Errors are inevitable, and the results of these direct measurements contain errors.
The calculation inevitably contains errors.
Indirect measurement method is
As a direct result, the relationship between the arithmetic mean values of various measurement parameters as functions can be obtained.
Indirect measurement.
Indirect measurement usually has two problems: one is known error measurement.
Find the indirect measurement error, that is, the error variable comes from
The number of emails seeking error is famous, and the other is to indirectly measure a given error value and find the allowable error after each direct measurement.
Find the function whose independent variable error is known.
2.4 Used to find and eliminate system errors.
Under certain test conditions, test methods and target stations
Instruments, usually before testing, are always affected by personal or small errors, and there are systematic error factors in solids.
The significance of legal events has great influence on the test system. In general, analysis and experiments should be carried out before testing to determine
These effects are eliminated from the causes or corrected.
Measure.
If the system error is reduced to its random error
Same size, no need to deal with system errors separately, unified use.
As a machine for handling errors.
However, in practice, the system error can not be completely eliminated. It may be that some obvious system errors are being measured.
Pity. In particular, the systematic error is also hidden in the random error, so it is also
The key problem is how to find the data to check whether there is a system error.
Poor, only by solving this problem, it is possible to further try to eliminate or correct it.
There are two kinds of system errors: fixed value and variable value, and their functions are different.
The systematic error of values affects the average value of repeated measurements, while
Does not affect the root mean square error. This will not only cause the random error distribution curve to change
Location, without affecting its distribution and the actual point is extraordinary.
Perimeter.
For different system errors, the magnitude and direction are different.
The measured image data of the effect is different, and there are also fixed methods.
This is not an accidental fluctuation.
If the system error value changes significantly, it will not only affect the weight
The average value of complex multiple measurements will affect every fixed rule.
Residual error and root mean square error. Therefore, it will not only change the distribution of random errors.
The position also makes the deformation distributed, which will make it.
The residual is not destructive, and it will also affect the actual distribution. Therefore,
Should provide the method to eliminate its causes, or obtain the variable value law of system error,
After all the measured data are corrected, the data count is corrected.
Calculate the measurement results and measurement errors.
For engineering survey, it only needs to meet the accuracy requirements, so there is no need to calculate and.
The specific error value of each measurement. When the accuracy of analysis, only
Precision encoder can be considered as the same as that measured by mechanical system.
Eliminate the errors caused by calibration.
In order to improve the accuracy of the measuring arm, a series of fuselage is designed.
Try to do the following:
1) at the meeting
On the premise of using the requirements of high-precision measurement of body stiffness, each mechanism should be as small and light as possible;
2) Adopt high-precision detection sensors, such as linear displacement measurement.
Grating angular displacement and code wheel.
3) Reasonable compensation for all kinds of mistakes.
Select the measuring arm according to three angles.
The measurement of the degree of freedom of the code disk requires 25,000 lines of code of the FLA series of the disk.
The error Δ 3 of disc 3 caused by encoding, the error of disc 2 is Δ 2, and discs 3 and 2 can cause the error of Δ 3+Δ 2. If the code disk 1
The total error caused by the error δ 1, and then caused by the 3-code disk. Δ=
Δ 12+(Δ2+Δ3)2
According to the measurement requirements, δ must be less than 20 microns and not exceed the maximum value.
50 microns.
If the minimum resolution m is set for the code wheel, then m =2π25000=
0.00025 1 rad. The precise coding disk depends on two aspects, one is the rigid code line.
Accuracy and the second output signal, when the output signal is positive.
String, the resolution of the encoder can be improved by 20 times, and the encoding disk at this time br/>; The real resolution of the actual electric meter = 0.000251/20 =1.255×10-5 rad,
These include:
Δ 12=( 1.255× 10-5×0.6)2
Δ2= 1.255× 10 -5×0.6
Δ3= 1.255× 10-5×0.3
δ= 13.364× 10-6M = 13.364 μm & lt； 20μm
The selected encoder can meet the measurement accuracy requirements.
References 1 Sun Editor-in-Chief Robot Control Technology Machinery Industry Press.
2 Cheng Daxian's mechanical design drawing (Volume 5) 3 Ma's mechanical industry press.
Yang Xinrong, Ling Yuhua and Ed are interested in modern technology and intelligent instrumentation and control technology.
Hunan science and technology publishing house
5. Research on the Theory and Application of Yang Xiulian's Robot Programming China Railway Publishing House.
7 [Japan] Xiong Fan />6. Robot Control Science Press