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

sensorModels/@sigmoidSensor/sigmoidSensor.m

@@ -0,0 +1,22 @@
+classdef sigmoidSensor
+    properties (SetAccess = private, GetAccess = public)
+        % Sensor parameters
+        alphaDist = NaN;
+        betaDist = NaN;
+        alphaPan = NaN;
+        betaPan = NaN;
+        alphaTilt = NaN; % degrees
+        betaTilt = NaN;
+    end
+
+    methods (Access = public)
+        [obj]               = initialize(obj, alphaDist, betaDist, alphaPan, betaPan, alphaTilt, betaTilt);
+        [values, positions] = sense(obj, agent, sensingObjective, domain, partitioning);
+        [value]             = sensorPerformance(obj, agentPos, agentPan, agentTilt, targetPos);
+        [f] = plotParameters(obj);
+    end
+    methods (Access = private)
+        x = distanceMembership(obj, d);
+        x = tiltMembership(obj, t);
+    end
+end