fig4
Figure 4. Optimization of coils. Magnetic flux density and performance of the traditional spiral coil (with uniform spacing) and the designed hybrid coils (with non-uniform spacing): (i) Patterns and (ii) simulation results of the magnetic flux density of (A) the traditional spiral and (B) the designed hybrid coil (k = 0.4). The right image in (ii) is the top-view magnetic flux densities for each type of coil; (C) Inductance changes as a function of displacements along the (i) z-axis and (ii) y-axis of tactile sensors based on different types of coils (a / A = 0.25). ΔLz1 and ΔLy1 represent changes of L1 along the z-axis and y-axis, respectively; (D) Illustration of the (i) coverage ratio and (ii) orientation of the top coil (red) relative to the bottom coils (blue). “a” represents the area of the top coil, and “A” represents the total area of the bottom coils; (E) Sensing performance for different coverage ratios: (i) Measured inductance changes along the z-axis and (ii) measured and calculated inductance changes along the y-axis; (F) Sensing performance for different orientations of the top coil: (i) Measured inductance changes along the z-axis and (ii) Measured and calculated inductance changes along the y-axis.
