Add OSQP as an alternative solver in the contacts computation

init.m

@@ -13,6 +13,7 @@
 %  */
 %% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 clear variables
+clear functions
 close all
 clc
 
@@ -34,6 +35,10 @@
 Config.GRAVITY_ACC = [0,0,-9.81];
 Config.tStep = 0.001;
 
+% Use qpOASES instead of quadprog, typically in the case where the optimization toolbox is not
+% available.
+Config.USE_OSQP = true;
+
 % Do you want to enable the Visualizer?
 confVisualizer.visualizeRobot = true;
 
@@ -47,4 +52,5 @@
 %% Init simulator core physics paramaters
 physics_config.GRAVITY_ACC = Config.GRAVITY_ACC;
 physics_config.TIME_STEP = Config.tStep;
+physics_config.USE_OSQP = Config.USE_OSQP;
 robot_config.SIMULATE_MOTOR_REFLECTED_INERTIA = Config.SIMULATE_MOTOR_REFLECTED_INERTIA;

lib/+wbs/@Contacts/Contacts.m

@@ -11,12 +11,14 @@
         is_in_contact = ones(8, 1); % this vector says if the vertex is in contact (1) or not (0)
         S; % selector matrix for the robot torque
         mu; % friction coefficient
-        A; b; Aeq; beq; % matrix used in the optimization problem
+        useOSQP; % Use the OSQP solver instead of quadprog for the optim. prob. computing the reaction forces at the feet
+        A; AxLb; AxUb; Aeq; beq; % matrices used in the optimization problem
+        osqpProb; % OSQP solver object
     end
 
     methods
 
-        function obj = Contacts(foot_print, robot, friction_coefficient)
+        function obj = Contacts(foot_print, robot, friction_coefficient,useOSQP)
             %CONTACTS The Contact class needs the coordinates of the vertices of the foot
             % Arguments
             %   foot_print - the coordinates of every vertex in xyz
@@ -30,6 +32,7 @@
             obj.S = [zeros(6, robot.NDOF); ...
                     eye(robot.NDOF)];
             obj.mu = friction_coefficient;
+            obj.useOSQP = useOSQP;
             obj.prepare_optimization_matrix();
         end
 
@@ -192,21 +195,42 @@
 
         function forces = compute_unilateral_linear_contact(obj, J_feet, M, h, torque, JDot_nu_feet, contact_point, generalized_ext_wrench)
             % compute_unilateral_linear_contact returns the pure forces acting on the feet vertices
-
+
+            persistent firstSolverIter;
+
+            if isempty(firstSolverIter)
+                firstSolverIter = true;
+            end
+
             free_acceleration = obj.compute_free_acceleration(M, h, torque, generalized_ext_wrench);
             free_contact_acceleration = obj.compute_free_contact_acceleration(J_feet, free_acceleration, JDot_nu_feet);
             H = J_feet * (M \ J_feet');
-
+            
             if ~issymmetric(H)
                 H = (H + H') / 2; % if non sym
             end
-
+            
             for i = 1:obj.num_vertices * 2
                 obj.Aeq(i, i * 3) = contact_point(i) > 0;
+%                 obj.Aeq(i,i*3-2:i*3) = contact_point(i) > 0;
+            end
+
+            if obj.useOSQP
+                if firstSolverIter
+                    % Setup workspace and change alpha parameter
+                    obj.osqpProb.setup(sparse(H), free_contact_acceleration, sparse([obj.A;obj.Aeq]), [obj.AxLb;obj.beq], [obj.AxUb;obj.beq], 'alpha', 1);
+                    firstSolverIter = false;
+                else
+                    % Update the problem
+                    obj.osqpProb.update('Px', nonzeros(triu(sparse(H))), 'q', free_contact_acceleration, 'Ax', sparse([obj.A;obj.Aeq]));
+                end
+                % Solve problem
+                res = obj.osqpProb.solve();
+                forces = res.x;
+            else
+                options = optimoptions('quadprog', 'Algorithm', 'interior-point-convex', 'Display', 'off');
+                forces = quadprog(H, free_contact_acceleration, obj.A, obj.AxUb, obj.Aeq, obj.beq, [], [], 100 * ones(24, 1), options);
             end
-
-            options = optimoptions('quadprog', 'Algorithm', 'interior-point-convex', 'Display', 'off');
-            forces = quadprog(H, free_contact_acceleration, obj.A, obj.b, obj.Aeq, obj.beq, [], [], 100 * ones(24, 1), options);
         end
 
         function [wrench_left_foot, wrench_right_foot] = compute_contact_wrench_in_sole_frames(obj, contact_forces, robot)
@@ -234,30 +258,43 @@
         end
 
         function prepare_optimization_matrix(obj)
-            % prepare_optimization_matrix Fills the matrix used in the optimization problem
-
+            % prepare_optimization_matrix Fills the matrix used by the optimization problem solver.
+            % A being the matrix of friction cone constraints, for ...
+            % - quadprog: Ax <= b (should include -x <= 0).
+            % - OSQP    : l <= Ax <= u (should include -Inf <= -x <= 0).
+            %
+            % So in both cases we define: AxLb <= Ax <= AxUb where AxLb = -Inf.
+
             total_num_vertices = obj.num_vertices * 2; % number of vertex per foot * number feet
-            num_variables = 3 * total_num_vertices; % number of unknowns - 3 forces per vertex
+            num_variables = 3 * total_num_vertices; % number of unknowns (3 force components per vertex)
             num_constr = 5 * total_num_vertices; % number of constraint: simplified friction cone + non negativity of vertical force
             % fill the optimization matrix
             obj.A = zeros(num_constr, num_variables);
-            obj.b = zeros(num_constr, 1);
+            obj.AxUb = zeros(num_constr, 1);
+            obj.AxLb = -Inf(num_constr, 1);
+
+            % Constraint "Fz=0 if no contact" formulated as Aeq x = 0.
+            % Aeq shall be concatenated with A in the case of OSQP.
             obj.Aeq = zeros(total_num_vertices, num_variables);
             obj.beq = zeros(total_num_vertices, 1);
-
-            constr_matrix = [1, 0, -obj.mu; ...% first 4 rows: simplified friction cone
-                        0, 1, -obj.mu; ...
-                            -1, 0, -obj.mu; ...
-                            0, -1, -obj.mu; ...
-                            0, 0, -1]; ...% non negativity of vertical force
-
+
+            constr_matrix = [...
+                1, 0, -obj.mu; ...% first 4 rows: simplified friction cone
+                0, 1, -obj.mu; ...
+                -1, 0, -obj.mu; ...
+                0, -1, -obj.mu; ...
+                0, 0, -1]; ...% non negativity of vertical force
+
             % fill a block diagonal matrix with all the constraints
             Ar = repmat(constr_matrix, 1, total_num_vertices); % Repeat Matrix for every vertex
             Ac = mat2cell(Ar, size(constr_matrix, 1), repmat(size(constr_matrix, 2), 1, total_num_vertices)); % Create Cell Array Of Orignal Repeated Matrix
             obj.A = blkdiag(Ac{:});
-
+
+            % Create an OSQP problem object
+            if obj.useOSQP
+                obj.osqpProb = osqp;
+            end
         end
-
     end
 
 end

lib/RobotDynamicsWithContacts/+robotDynWC/step_block.m

@@ -21,7 +21,7 @@
 
         function setupImpl(obj)
             obj.robot = wbs.Robot(obj.robot_config,obj.physics_config.GRAVITY_ACC);
-            obj.contacts = wbs.Contacts(obj.contact_config.foot_print, obj.robot, obj.contact_config.friction_coefficient);
+            obj.contacts = wbs.Contacts(obj.contact_config.foot_print, obj.robot, obj.contact_config.friction_coefficient,obj.physics_config.USE_OSQP);
             obj.state = wbs.State(obj.physics_config.TIME_STEP);
             obj.state.set(obj.robot_config.initialConditions.w_H_b, obj.robot_config.initialConditions.s, ...
                 obj.robot_config.initialConditions.base_pose_dot, obj.robot_config.initialConditions.s_dot);

lib/RobotDynamicsWithContacts/loadRobotDynamicsWithContactsCB.m

@@ -1,3 +1,12 @@
 % Add path to local source code, and parent folder for the making the dependencies classes package
 % visible to MATLAB path.
 addpath(strcat(fileparts(mfilename('fullpath')),'/..'));
+
+% set paths to the osqp-matlab library
+osqp_libraryPath=getenv('OSQP_MATLAB_PATH');
+if exist(osqp_libraryPath, 'dir')==7
+    addpath(genpath(osqp_libraryPath));
+    disp('Added osqp-matlab library');
+else
+    error([osqp_libraryPath,': Path directory non existent!']);
+end