  Bio-hybrid systems---close couplings of natural organisms with
technology---are high potential and still underexplored. In existing work,
robots have mostly influenced group behaviors of animals. We explore the
possibilities of mixing robots with natural plants, merging useful attributes.
Significant synergies arise by combining the plants' ability to efficiently
produce shaped material and the robots' ability to extend sensing and
decision-making behaviors. However, programming robots to control plant motion
and shape requires good knowledge of complex plant behaviors. Therefore, we use
machine learning to create a holistic plant model and evolve robot controllers.
As a benchmark task we choose obstacle avoidance. We use computer vision to
construct a model of plant stem stiffening and motion dynamics by training an
LSTM network. The LSTM network acts as a forward model predicting change in the
plant, driving the evolution of neural network robot controllers. The evolved
controllers augment the plants' natural light-finding and tissue-stiffening
behaviors to avoid obstacles and grow desired shapes. We successfully verify
the robot controllers and bio-hybrid behavior in reality, with a physical setup
and actual plants.
