diff --git a/swarm_robot_simulation/src/two_wheel_robot_aggregation.cpp b/swarm_robot_simulation/src/two_wheel_robot_aggregation.cpp
index 6a4598a..43976c2 100644
--- a/swarm_robot_simulation/src/two_wheel_robot_aggregation.cpp
+++ b/swarm_robot_simulation/src/two_wheel_robot_aggregation.cpp
@@ -1,7 +1,12 @@
 // this node is the aggregation simulation of two wheel robots
 
 // aggregation algorithm:
-
+// This simulation aggregates a swarm of two wheel robots by a geometric center method. Each robot
+// calculates the geometric center of all its neighbors in the sensing range. The first feedback vector
+// starts from the robot to the geometric center. In order to avoid collision, a spring model with only
+// propulsional force (the spring only pushes two robots away, not drag them together) is used for all
+// neighbors with distance smaller than spring length. This is the second feedback vector. Then two feedback
+// vector will be fused into one with weighted ratio.
 
 // subscribe to topic "/swarm_sim/two_wheel_robot"
 // service client to service "/gazebo/set_joint_properties"
diff --git a/swarm_robot_simulation/src/two_wheel_robot_dispersion.cpp b/swarm_robot_simulation/src/two_wheel_robot_dispersion.cpp
index 5e57d7c..d0468a0 100644
--- a/swarm_robot_simulation/src/two_wheel_robot_dispersion.cpp
+++ b/swarm_robot_simulation/src/two_wheel_robot_dispersion.cpp
@@ -3,7 +3,13 @@
 // this is the first simulation program written for two wheel robots
 
 // dispersion algorithm explanation:
-
+// This simulation uses the force feedback from a spring model to control the speed and moving direction
+// of the robots. The key is to decide which robots will be the neighbors. In the sensing range of one
+// robot, all robots of distances within the spring length plus a small portion of spring length are
+// qualified. If the number exceed a defined upper limit (6 for example), the closest 6 will be chosen.
+// If the number is smaller than a defined lower limit (3 for example), the distance constraint will be
+// overrode, and trying to get as much neighbor number as the define lower limit if possible (within
+// sensing range). Then calculating the feedback vector based on the spring force.
 
 // subscribe to topic "/swarm_sim/two_wheel_robot"
 // service client to service "/gazebo/set_joint_properties"
diff --git a/swarm_robot_simulation/src/two_wheel_robot_line_formation.cpp b/swarm_robot_simulation/src/two_wheel_robot_line_formation.cpp
index 61eb0c3..e1a239f 100644
--- a/swarm_robot_simulation/src/two_wheel_robot_line_formation.cpp
+++ b/swarm_robot_simulation/src/two_wheel_robot_line_formation.cpp
@@ -1,7 +1,15 @@
 // this node is the line formation simulation of two wheel robots
 
 // line formation algirithm explanation:
-
+// This simulation forms a line by using a local line fitting technique. Each robot does a linear fitting
+// on all its neighbor robots in the sensing range. Then calculating two feedback vectors to drive the
+// robot into its fitted line: perpendicular feedback vector and parallel feedback vector. Perpendicular
+// feedback vector starts from the robot to the perpendicular point on the fitted line. Computation of
+// parallel feedback vector needs two neighboring robot. These two neighbors locates at the left and right
+// of the robot, they have the smallest distance to the perpendicular line. It's OK that the left or
+// right robot is missing (or both). Neighbors' distance to the perpendicular will be calculate the parallel
+// feedback vector as in the spring model. Then two feedback vector will be fused into one with weighted
+// ratio.
 
 // subscribe to topic "/swarm_sim/two_wheel_robot"
 // service client to service "/gazebo/set_joint_properties"