Sensor-based complete coverage path planning in dynamic environment for cleaning robot

Using Complete Coverage Path Planning （CCPP）, a cleaning robot could visit every accessible area in the workspace. The dynamic environment requires the higher computation of the CCPP algorithm because the path needs to be replanned when the path might become invalid. In previous CCPP methods, when the neighbours of the current position are obstacles or have been visited, it is challenging for the robot to escape from the deadlocks with the least extra time cost. In this study, a novel CCPP algorithm is proposed to deal with deadlock problems in a dynamic environment. A priority template inspired by the short memory model could reduce the number of deadlocks by giving the priority of directions. Simultaneously, a global backtracking mechanism guides the robot to move to the next unvisited area quickly, taking the use of the explored global environmental information. What＇s more, the authors extend their CCPP algorithm to a multi-robot system with a market-based bidding process which could deploy the coverage time. Experiments of apartment-like scenes show that the authors＇ proposed algorithm can guarantee an efficient collision-free coverage in dynamic environments. The proposed method performs better than related approaches on coverage rate and overlap length.

The Tessellation Rule and Properties Programming of Origami Metasheets Built with a Mixture of Rigid and Non-Rigid Square-Twist Patterns

Metamaterials constructed from origami units of different types and behaviors could potentially offer a broader scope of mechanical properties than those formed from identical unit types.However,the geometric design rules and property programming methods for such metamaterials have yet to be extensively explored.In this paper,we propose a new kind of origami metasheet by incorporating a family of different square-twist units.The tessellation rule of these metasheets is established to allow compatible mountain-valley crease assignments and geometric parameters among neighboring units.We demonstrate through experiments that the energy,initial peak force,and maximum stiffness of the metasheets can be obtained by a summation of the properties of the constitutional units.Based on this,we are able to program the mechanical properties of the metasheets over a wide range by varying the types and proportions of the units,as well as their geometric and material parameters.Furthermore,for a metasheet with a fixed number of units,all the geometrically compatible tessellations can be folded out of the same pre-creased sheet material by simply changing the mountain-valley assignments,thereby allowing the properties of the metasheet to be re-programmed based on specific requirements.This work could inspire a new class of programmable origami metamaterials for current and future mechanical and other engineering applications.

Folding of Tubular Waterbomb

Origami has recently emerged as a promising building block of mechanical metamaterials because it offers a purely geometric design approach independent of scale and constituent material.The folding mechanics of origami-inspired metamaterials,i.e.,whether the deformation involves only rotation of crease lines(rigid origami)or both crease rotation and facet distortion(nonrigid origami),is critical for fine-tuning their mechanical properties yet very difficult to determine for origami patterns with complex behaviors.Here,we characterize the folding of tubular waterbomb using a combined kinematic and structural analysis.We for the first time uncover that a waterbomb tube can undergo a mixed mode involving both rigid origami motion and nonrigid structural deformation,and the transition between them can lead to a substantial change in the stiffness.Furthermore,we derive theoretically the range of geometric parameters for the transition to occur,which paves the road to program the mechanical properties of the waterbomb pattern.We expect that such analysis and design approach will be applicable to more general origami patterns to create innovative programmable metamaterials,serving for a wide range of applications including aerospace systems,soft robotics,morphing structures,and medical devices.

A Humidity-Powered Soft Robot with Fast Rolling Locomotion

A range of soft robotic systems have recently been developed that use soft,flexible materials and respond to environmental stimulus.The greatest challenge in their design is the integration of the actuator,energy sources,and body of robots while achieving fast locomotion and well-defined programmable trajectories.This work presents such a design that operates under constant conditions without the need for an externally modulated stimulus.By using a humidity-sensitive agarose film and overcoming the isotropic and random bending of the film,the robot,which we call the Hydrollbot,harnesses energy from evaporation for spontaneous and continuous fast self-rolling locomotion with a programmable trajectory in a constant-humidity environment.Moreover,the geometric parameters of the film were fine-tuned to maximize the rolling speed,and the optimised hydrollbot is capable of carrying a payload up to 100%of its own weight.The ability to self-propel fast under constant conditions with programmable trajectories will confer practical advantages to this robot in the applications for sensors,medical robots,actuation,etc.