fixed issues in sigmoid sensor model causing inverted response (annular partitions)

sensorModels/@sigmoidSensor/distanceMembership.m

@@ -0,0 +1,10 @@
+function x = distanceMembership(obj, d)
+    arguments (Input)
+        obj (1, 1) {mustBeA(obj, 'sigmoidSensor')};
+        d (:, 1) double;
+    end
+    arguments (Output)
+        x (:, 1) double;
+    end
+    x = 1 - (1 ./ (1 + exp(-obj.betaDist .* (abs(d) - obj.alphaDist))));
+end