This study proposes a method for 3D modeling of weft knitted fabric and simulating its deformation behavior. A geometric model of the fabric was established using a loop-mesh unit, and the surface of the yarn was calculated using a reference frame. The patterns of the fabrics were represented by bitmap images. To simulate the deformation behavior of the fabric, a physical model was built based on a dynamic spline that included stretching and bending of the yarn. To simplify the collisions between continuous yarns, collisions were detected using a discrete sphere-spring model. The Euler-Lagrange theorem was introduced to achieve the energy balance of the system, and a stable shape was obtained by solving the Euler-Lagrange equation explicitly according to the convergence conditions. Rendering and deformation of the model were implemented using a simulator program via C++ and OpenGL. The simulation displayed the 3D appearance of the weft knitted fabric. The deformed shapes of fabrics were accurately predicted by the proposed method.

Weft-knitted fabric is formed by interlocking loops, which results in an unstable and easily deformable structure. In particular, fancy weft-knitted fabric exhibits diverse structural variations and uneven distribution, leading to more prominent characteristics of instability and deformation. Achieving the desired pattern effect and dimensions often requires drawing multiple designs. In this work, to obtain the geometric model of fancy fabric, mesh-loop models with movement vectors are established based on the basic structure of four stitch types: plain stitch, tuck, float, and loop transfer. The cubic Catmull–Rom spline curves are used to fit the geometric centerline of the yarn. The movement vectors are used to represent the changes in the position of the key points of the standard loops in the fancy fabric, which are derived from the analysis of the pattern grid. A physical model is established based on the force analysis of the yarn, and the positions of yarn control points are determined by solving the Euler–Lagrange dynamic equations. Through iterative calculations, the deformation effects of the fabric are obtained, enabling the simulation of fancy weft-knitted fabric. The proposed algorithms were implemented using Visual C++. The reliability and accuracy of the simulation method are demonstrated by comparing the contours of the simulation results with the actual samples.

In order to solve the problem of low response frequency and poor consistency of conventional yarn grippers in weft accumulators, in this study, a piezoelectric yarn gripper is used instead of conventional yarn grippers and the motion characteristics of its actuator are studied. This gripper uses a bimorph piezoelectric bending actuator with a low-cost, well integrated self-sensing method based on charge measurement. The modeling of the piezoelectric micromanipulator is based on the piezoelectric and Euler–Bernoulli beam equations. The static and dynamic characteristics of the piezoelectric actuator as well as the self-sensing capability were experimentally tested. The experimental results show that the maximum output displacement at the end of the piezoelectric actuator is 834 μm, and the maximum output force is 388 μN at 150 V driving voltage. The stability and consistency of its response are also very good, with a response speed of 24 ms. The self-sensing test of the output force also proved the feasibility of the self-sensing method used, with an error of 0.74%. The piezoelectric yarn gripper studied in this paper is promising for practical clamping applications.

The yarn feeding for a loop formation is a critical factor in determining the size and elasticity of highly elastic knitted fabrics. Currently, the prevalent production processes rely on experienced machine operators to set up the optimal feed rate by trial and error. To improve production efficiency and reduce the reliance on the operator’s skill, we attempt to create a structure model of tubular knitted fabric that could correlate the size as well as elasticity of fabric with the loop geometry parameters (wale spacing, course spacing) of the yarn feeding. The experimental tensile test of the elastic fabric verified that the model is able to deduce the yarn feeding parameters from the elasticity and dimensional requirements of the fabric to be knitted. It is also illustrated that the yarn feeding is a key factor in controlling the elasticity of knitted fabrics.

Aiming at the problem of the malfunction of knitting machines caused by the unstable operation of the piezoelectric needle selector during the jacquard process, a state detection scheme for the piezoelectric needle selector that integrates the sensor and drive function co-located is proposed. The motion state of bimorph piezoelectric cantilever beam and its bi-directional piezoelectric effect in the jacquard process of piezoelectric needle selector are analyzed. Electrical and dynamic models were established for the electrical characteristics inside the bimorph piezoelectric cantilever beam and the dynamic characteristics of the cutter head and baffle of the needle selector. The signal detection circuit is designed to realize the real-time detection of the piezoelectric needle selector state by analyzing the time domain and frequency domain characteristics of the electrical signal. The results show that in the normal working state of the piezoelectric needle selector, the internal electric signal of the piezoelectric driver has two characteristic frequencies, which are between 155 and 180 and between 1630 and 1670 Hz, and the time for the piece to swing to the limit position is relatively long under abnormal working conditions.