| Multi-degree-of-freedom displacement measurement is an important means to obtain the target pose,which is widely used in industrial production and scientific research,such as semiconductor processing positioning,aircraft flight attitude detection,manipulator end pose measurement,etc.According to the different number of sensors used,the multiDOF displacement measurement methods are mainly divided into two categories: The first type is realized by combining multiple displacement sensors.This method has Abbe errors,large multi-axis cumulative errors,and huge measurement systems,it's complicated and difficult to install;the second type is to realize the measurement of multidegree-of-freedom displacement through a single displacement sensor,this type of sensor has small cumulative error,simple structure and convenient installation.Regardless of the first or second type,the laser interferometer and capacitive type are mainly used.The laser interferometric measurement has high accuracy,fast speed,and large stroke,but it has harsh environmental requirements.Although the capacitive displacement sensor has high accuracy and simple structure,the stroke is too small,which limits its application range.Therefore,it is extremely urgent to design a new type of sensor with simple structure,wide application range,and multi-degree-of-freedom displacement measurement.This paper firstly analyzes the research background and significance of the subject and the research status of multi-degree-of-freedom displacement measurement technology at home and abroad,and puts forward the research content of this paper: a flexible displacement sensor that can realize X-Y-Z-?_z four-DOF displacement measurement.Second,analyze and compare the advantages and disadvantages of various displacement detection principles and application scenarios,combined with the application scenarios and purposes of the subject,determine that the four-degree-offreedom flexible displacement sensor adopts the principle of resistance strain type.The measurement theory of linear displacement X,Y,Z,angular displacement ?_z and the deformation of the elastic body are analyzed.According to the characteristics of each strain gauge and the deformation of the elastic body,two types of resistance strain gauges used in the sensor are determined.Then,the strain gauge layout and measurement circuit of the four displacement parameters of the sensor are designed,so that the sensor can realize the measurement of the four displacement parameters of X,Y,Z,?_z and the output between each displacement is basically without interference.And increase the output sensitivity,realize the temperature compensation.And then,in order to verify the effectiveness of the proposed multi-degree-offreedom displacement detection method,a four-free displacement measurement system was built and related tests were carried out.Mainly include: 1)A method for batch pasting of strain gauges is proposed,which can realize the one-time pasting of strain gauges on the elastic body of the sensor,ensuring the position and angle requirements between the strain gauges;2)Setting up a test system,displacement and The trajectory is accurately controlled by the ABB Delta robot,equipped with a 32-channel strain gauge with a data acquisition system,which can realize the simultaneous measurement of multiple displacement parameters;3)The four displacement parameters were tested separately,and a better solution was provided for the nonlinearity and large hysteresis of the sensor;4)Analyzed the coupling output situation of other displacement channels when the four displacement parameters act independently.Finally,the sensor is statically decoupled and the main static performance parameters are tested.The hysteresis characteristics of the sensor make the positive and negative strokes of the sensor need to be decoupled.Aiming at the nonlinearity of the sensor,a static nonlinear decoupling algorithm based on coupling error modeling is proposed,and it is compared with two static linear decoupling algorithms based on Kramer's rule and solving generalized inverse matrix.Experimental results show that the static nonlinear decoupling algorithm based on coupling error modeling proposed in this paper is significantly better than the other two decoupling algorithms and the decoupling effect is significant.After using this decoupling algorithm,the average measurement errors of X,Y,Z,and ?_z are 1.98%,2.45%,0.81%,0.92% respectively.When multiple displacement parameters are combined,the sensor can also accurately measure each displacement parameter,and the average measurement error is less than 4%. |
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