Resolving conflicts

demo2.m

@@ -190,6 +190,9 @@
         zdot = q_sol(k,2) - ( (q_sol(k,3)*abs(q_sol(k,2))*sigma_0) / ...
                (Fc+(Fs-Fc)*exp(-(q_sol(k,2)/vs)^2)) );
         F(k) = sigma_0*q_sol(k,3) + sigma_1 * zdot + sigma_2*q_sol(k,2);
+
+        % When motion occurs, the resulting force suddenly drops
+        % See Fig. 6 (bottom figure)
         if (k>1) && (F(k)-F(k-1)<0)
             break;
         end

sim_stick_slip.m

@@ -1,15 +1,17 @@
 function [xdot, zdot, F] = sim_stick_slip(t, q, M, Fs, Fc, sigma_0, sigma_1, sigma_2, vs)
-
-
-    k = 2;            % stiffness of the spring
-    y = 0.1*t;        % 0.1 m/s
-    u = k * (y - q(1,:)); % force by the spring
+
+    k = 2;                  % stiffness of the spring
+    y = 0.1*t;              % 0.1 m/s
+    u = k * (y - q(1,:));   % force by the spring
 
-    zdot = q(2,:) - ( (q(3,:).*abs(q(2,:))*sigma_0) ./ (Fc+(Fs-Fc)*exp(-(q(2,:)/vs).^2)) );
+    zdot = q(2,:) - ( (q(3,:).*abs(q(2,:))*sigma_0) ./ ...
+           (Fc+(Fs-Fc)*exp(-(q(2,:)/vs).^2)) );
+
     F = sigma_0*q(3,:) + sigma_1 * zdot + sigma_2*q(2,:);
 
     qdot_1 = q(2,:);
     qdot_2 = (u - F) / M;
     qdot_3 = zdot;
     xdot = [qdot_1 ; qdot_2; qdot_3 ];
+
 end