Hardware and Signal Processing for a Novel Multi-Lap-Joint Measurement System for Automated Welding Applications

Position gauging of welding joints with an FMCW-based mm-wave radar system

“…Hence, it can be assumed that only the main edge or corner is illuminated by the system. As described in [1], only cross-polarized scattering effects of the targets are used for PoE. All geometries (lap joint, V-butt joint, and T-joint) introduce local polarimetric effects that occur at spatial discontinuities such as edges, wedges, or corner reflectors [23].…”

“…Figure 5 shows one prototype frontend (FE). For the sake of self-containment, the basic parts of the FE are recapitulated here (a detailed description can be found in [1]). A 77 GHz voltage-controlled oscillator (VCO #5), stabilized in a phase-locked loop (PLL) #6 generates the radio frequency signals.…”

“…Before the position of the weld can be estimated, the measured data must be preprocessed; more specifically, the 2D-measured data sets x ( u x , k r ) are reduced to 1D. In the basic form, as described in [1], x ( u x , k r ) is Fourier-transformed and scaled to range. Then | x ( u x , R )| is calculated and summed up over all positions u x .…”

“…A major challenge in system engineering is to find novel applications and concepts for different measurement scenarios and detecting tasks [1]. In addition, these concepts should push the limits of present available systems in technical aspects such as accuracy, flexibility, reliability, and in economical demands, for instance, low-cost solutions, low maintenance requirements, and environmental friendliness.…”

“…Since these effects are strongly locally bounded to the discontinuities, higher accuracy can be achieved by using a cross-polarized approach for position estimation (PoE) compared with a co-polarized one. We have already demonstrated the functionality of the basic principle and that radar sensors work reliably during a welding process in [1]. There, the basic measurement scenario and the signal processing focused on the most common welding geometry, namely a lap joint is presented.…”