title: Perceiving and manipulating liquids and transparent objects
Creators: name: Do, Chau
Publisher: name: Albert-Ludwigs-Universität Freiburg
Year: 2020
Subjects: subject: 000

description: Over the past few years, the presence of robots in our homes has increased, with vacuuming and companion robots becoming more popular. A home environment is particularly difficult for a robot to operate in due to its variability and lack of structure. Ideally, when we think of service robots, we envision them taking over mundane tasks such as cooking and cleaning. However, many challenges still remain before this is fully realized. In this thesis we present approaches, which enable a robot to handle liquids and transparent objects, both of which are commonly found in home environments. Specifically, for liquids we look at detecting the liquid height in cups as well as pouring the liquid to user defined heights, while avoiding spillage and collisions. We also present an approach for detecting transparent objects, which is a necessary first step for grasping and collision avoidance. Both liquids and transparent objects are more problematic than standard objects, due to factors such as non-rigidity and transparency. The methods we present here provide robots with the skills for dealing with them, which is essential to completing common daily tasks. Handling liquids is necessary in many tasks such as cooking a meal or just simply pouring a drink. Liquids are difficult due to the variation in their characteristics such as color and viscosity. Additionally, they are non-rigid, making it harder for a robot to interact with them. In this thesis, we look at the problem of pouring liquids and break it down into sub-problems. First, we present an approach for detecting the liquid level in a cup. In this scenario, the liquid is static, so no pouring occurs. A robot must first perform this step to avoid pouring into an already full cup or possibly to modify how it transports an empty versus a full cup. Our approach does not require any previous knowledge of the liquid and can handle various types of liquids. Building on this, we present a method for detecting the liquid level during a pour. This scenario is different in that the liquid level must be detected quickly enough to allow modifications in the pouring motion. Next, we focus on the problem of pouring a liquid to specific heights while avoiding spillage and collisions. For this, we present an approach for learning the pouring trajectory which considers each of these goals. Finally, we look at transparent objects, which are problematic due to their changing appearances in different environments. Due to their pervasive presence in homes, it is important for a service robot to properly handle them. We present an approach capable of segmenting novel transparent objects in different environments, with other opaque objects present. In this work, we focus on approaches dealing with difficult objects found in a household. We presented approaches, which will assist robots in completing common tasks expected of a human. For each of our approaches, we conducted experiments and compared them to previous works. Our results showed improvements over existing methods, which reinforces their contribution. The work presented here takes a step forward towards the goal of having fully autonomous service robots in our homes.