Fix broken links in documentation

Author: dmronga

index.md

@@ -2,15 +2,14 @@
 
 ### Whole-Body Control
 
-Whole Body Control (WBC), also referred to as constraint-based or optimization-based control, is an approach for specifying and controlling complex robotic tasks. 
-The term was coined by Luis Sentis in his work
+Whole Body Control (WBC) is an approach for specifying and controlling complex robotic tasks
 [Synthesis and Control of Whole-Body Behaviors in Humanoid Systems](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.73.8747&rep=rep1&type=pdf).
 
 <img src="images/wbc_principle.svg" alt="drawing" width="600"/>
 
 Image Credits: Dennis Mronga, DFKI
 
-The idea is define a set of feedback controllers around an optimization problem. Each controller regulates a certain task, the control output is fed into the cost function of the optimization problem, typically a quadratic program, and thus minimized during execution.
+The idea is to define a set of feedback controllers around an optimization problem. Each controller regulates a certain task, the control output is fed into the cost function of the optimization problem, typically a quadratic program, and thus minimized during execution.
 In each control cycle ...
   * The cost function is updated with the current robot state and controller reference
   * The optimization problem is solved
@@ -52,7 +51,6 @@ The design of WBC library separates the whole-body controller into 4 main buildi
 # Installation
  * [WBC Library](installation/installation_no_rock.md)
  * [ROS2 Interface](installation/installation_ros2.md)
- * [Rock Interface](installation/installation_rock.md)
 
 # Testing
 

installation/installation_rock.md

@@ -12,7 +12,7 @@ You should now see the KUKA iiwa robot in rviz. The robot maintains a fixed end
 <br/>
 <br/>
 
-In the [nullspace_example.launch.py](https://github.com/ARC-OPT/wbc_ros/blob/main/launch/nullspace_example.launch.py) file, the code to load the example is explained step by step. This [iiwa_controllers.yaml](https://github.com/ARC-OPT/wbc_ros/blob/main/config/nullspace_example/iiwa_controllers.yaml) file describes the ros2 control configuration, which is loaded in the launch file. 
+In the [nullspace_example.launch.py](https://github.com/ARC-OPT/wbc_ros/blob/main/launch/null_space_example.launch.py) file, the code to load the example is explained step by step. This [iiwa_controllers.yaml](https://github.com/ARC-OPT/wbc_ros/blob/main/config/null_space_example/iiwa_controllers.yaml) file describes the ros2 control configuration, which is loaded in the launch file. 
 
 If you type `ros2 control list_controllers` you can see the available controllers: 
 ```!bash