Sewer system infrastructure requires huge capital to establish and maintain. Although they are meant to last for decades, drainage systems deteriorate with time due to aging, overloading, misuse, and mismanagement. Sewers can collapse and create a sinkhole if the condition assessment of the pipes is not done properly. One of the reasons for the generation of voids and cracks is continuous water flow in the pipe washes away the surface of the pipe from inside. A Weak foundation around the sewer pipe also increases the chances of collapsing. TISCALI project (Technology Innovation for Sewer Condition Assessment – Long-Distance Information-system) aims to create an objective quantification of the defects in sewer pipes and to determine their structural strength and stability.
One way to assess the condition of the sewer pipe is by mobilizing an in-pipe inspection robot to locally quantify sewer conditions. The robot used in TISCALI project uses the impact-echo method to excite the sewer with the prescribed energy and for a certain duration by the means of an impactor developed in the Robotics and Mechatronics (RaM) group and to analyze pipe's acoustic/mechanical response to this excitation. The current version of the robot has the capability to perform the impactor-echo experiment at every angle inside the pipe. It has a mechanism that lifts the impactor-echo setup to the desired height to carry out the experiment. The robot can operate in pipe diameters ranging from 300 mm to 500 mm. Some limitations of the robot are that it cannot move by itself, there is some slagging in the center lead shaft due to the reaction force from the impact, and all three legs do not apply equal force to remain in contact with the sewer wall.
The aim of this master assignment is to improve the dynamic performance of the robot that carries the impactor-echo setup. The robot has three links with a rolling point contact with the sewer wall. A variable stiffness needs to be incorporated in the link supporting the legs which will ensure that all legs exert an equal amount of force to stay in contact with the wall. It can be achieved either by changing the structure of the robot or by feedback control. The weight of the impactor-echo setup induces bending in the rod on which the whole setup lies. A way to reduce or remove this slagging needs to be found out. Also, accurate positioning of the impactor-echo setup with a proximity sensor will be implemented.