Variable Topology Trusses (VTT) are a new class of self-reconfigurable robot. A VTT consists of linear actuators for the truss members, which are joined at the truss nodes by a special reconfigurable spherical joint. The VTT can reconfigure by merging and splitting these truss nodes.

## Research Projects

#### Motion Planning for Variable Topology Truss Modular Robot

*Proc. RSS 2020*

We present a motion planning framework to do geometry reconfiguration and topology reconfiguration for a Variable Topology Truss (VTT). The problem is difficult because its configuration space is complicated and motion of nodes are strongly coupled. With our approach, we can apply sampling-based planner efficiently for geometry reconfiguration by significantly decreasing the search space and simplified collision model. For topology reconfiguration, we provide an algorithm to compute all partitioned enclosed subspaces and a graph search algorithm can be applied efficiently to search a sequence of topology reconfiguration actions.

#### A Fast Configuration Space Algorithm for Variable Topology Truss Modular Robots

*Proc. ICRA 2020*

We present a fast algorithm to compute the configuration space for a node in a Variable Topology Truss (VTT). A VTT is usually composed of multiple edge modules or members resulting in a high degrees-of-freedom (DOFs) system. Also members forming VTT structure typically span the workspace in a very non-uniform manner as the truss configuration creates a complicated configuration space. With our approach, the configuration space of a given node, including its free space and obstacle region, can be computed efficiently which can be further decomposed into multiple convex cells and path planning can be solved efficiently using graph search algorithm.

#### Reconfiguration Planning for Variable Topology Truss

*Proc. IROS 2019*

**Finalist for Best Paper Award on Safety, Security, and Rescue Robotics in Memory of Motohiro Kisoi at IROS 2019**

We propose a novel motion planning algorithm for modular robots to handle this problem with huge state space inspired by DNA replication process — the topology of DNA can be changed by cutting and resealing strands as tanglements form. In a variable topology truss, a single node with enough edge modules can split into a pair of nodes and two separate nodes can be merged to become an individual one. A novel way to model the robot in a nonuniform grid space is presented and a simple local planner is also developed to check the validation of possible actions.

#### Variable Topology Truss: Design and Analysis

*Proc. URAI 2017 and Proc. IROS 2017*

Related to an existing class of robots, the variable geometry truss (VGT), variable topology trusses have the additional capability to change the topology of the truss through self-reconfiguration. The hardware necessary to achieve this is introduced, and the constraints and capabilities of this new type of robot are analyzed by introducing the concept of a topology neighbor graph. Lastly, the minimal reconfigurable VTTs, which require 18 members, are identified and their achievable topologies are enumerated.