A Reconfigurable Robotic System Using an Interbody Wire for Merging and Cooperative Tasks

“

A single rope, two robots can both merge and work together separately.

The direction of reconfigurable robots is not unfamiliar to everyone.

M-TRAN

、

Roombots

This type of modular robot can change into different forms by assembling modules, from mobility to operation.

However, a team from the University of Tokyo noticed that the modules in such systems

mostly

are mechanically

fixed connections, and the research focus has mainly been on the functionality of the single body after connection.

When the modules are separated and scattered in space, the relationship between them is rarely considered as a usable function.

Therefore, they published their new work in the

Advanced Intelligent Systems

journal TwinX:

Two wheeled leg robots, connected by a

inter-robot rope

（

interbody wire),.

Two robots can both merge and work together separately.

For example, after merging, they can pick up an online food bag and then throw it into the trash can:

The inter-robot rope circles around and drags large-range trash:

Using the inter-robot rope to hook and transport objects, as well as force transmission on steep slopes:

TwinX

Composed of two hardware-identical wheeled leg robots

WiXus, named by color WiXus-Red and the WiXus-Blue. The rope extends from the Blue central spooling module, wraps around the Red central staircase bolt about five turns, and is tied with a bowline knot to the front suspension nut. According to Euler's belt theory, the friction generated by winding can make this nut basically not bear significant tensile force.

The rope used is about

2.0mm

in diameter Dyneema rope, the spooling module

has a maximum continuous tensile force of about

313N

and a maximum reeling length of about

. It should be noted that the rope tension values given in the paper are estimated values based on motor current calibration.

The problem is that the rope can only transmit tension and cannot withstand bending and torsion. Therefore, the team added a docking interface on the body:

Blue

One side has four holes, Red the other side has four docking pins. The pin diameter 10mm and hole diameter 10.3mm, after rounding the hole mouth and expanding to 16.3mm, the pin tip is cut to 3.5mm, so that alignment does not require too high positional accuracy Tightening the rope allows merging, forming three body configurations in one set.

01.

Tightening the rope causes the body to merge, forming three body forms in one set

The final body configuration depends on which two faces are docked The final form it becomes depends on which two faces are connected.

Each unit

WiXus

Docking results in a four-legged configuration A 、 B Two connecting faces allow the rope to move through a shared groove between the two faces. By rotating the fuselage using the pitch joint on the wheel legs, you can choose which face to connect.

A–A

structure, same as common four-legged robots;

Docking results in a steering wheel (

Roll–Pitch–Pitch

) configuration

B–B, each wheel can independently steer, allowing omnidirectional movement; swerve drive After docking, standing upright, with the body below, it becomes a mobile operation robot B–A, with two Blue arms mounted on a differential two-wheel chassis., differential two-wheel chassis with two Yaw–Pitch–Pitch When stationary, the.

Blue

camera identifies

Red

three

D455

Camera recognition

Blue

three on the body

AprilTag

markers (two for long-range recognition, one for short-range recognition), the controller first moves the body to the target pose nearby, with distance error less than

0.08

a corresponding estimated tension current command is continuously sent to the spooling motor

Red

to prevent the rope from loosening

Blue

continuously giving the spool motor a corresponding about

15N, and the steering wheel configuration corresponds to about, used to prevent the two robots from separating.

134N

When testing on real hardware, 224N the two 187N each run a complete strategy, only executing the outputs for their own legs, and exchange observation data between the two sides. The real hardware communication delay is about, and during training, random delays of about two units WiXus seconds, the system will automatically stop.

In outdoor field tests, the four-legged configuration of the

UDP

walked on grass, downstairs, and across the curb in three scenarios, and

5ms

did not fall over

40ms

delay to simulate. If more than

seconds no data is received from the other side, the system will automatically stop.

After separation, this rope can still be used to carry, hook, and pull

TwinX

in three scenarios: walking on grass, going down stairs, and crossing a curb, the calculation for the steering wheel configuration can be completed separately by each wheel, and no communication is needed between the two robots this rope remains an active reeling and releasing connection that can be directly used for work.

The calculation for the rudder wheel configuration can be completed separately for each wheel, and communication between the two robots is not required.

The team also performed a garbage collection task: first using the rudder wheel configuration to move forward, disengaging the docking, switching the docking surface, re-docking, and transforming into a mobile operation configuration. The two arms then pick up the garbage and throw it into the trash bin, before reverting back to the rudder wheel configuration to move away. Throughout the task, the docking control was executed twice, both times successfully completed, and at the start of each instance, the orientation of the two robots was already roughly aligned.

02.

The robots remain stationary, TwinX More interestingly, after the two robots separated, to avoid the rope sagging and falling to the ground. After enclosing, the two robots move in the same direction, dragging the pile of garbage of various sizes and shapes in one go.

The second task was

to hook ".

Red

remained stationary, Blue to avoid the rope sagging and falling to the ground. After enclosing, the two robots moved in the same direction, performing the rope release positioning, bringing the rope to the bottom of the three watering cans, then tightening the rope, and the two robots then used their leg joints to lift the body, making the tight rope 0 to prevent the rope from becoming slack and falling to the ground. After the rope was properly secured, the two robots moved in the same direction, and the reeling in the rope while moving towards.

to keep the watering cans suspended, and finally, the two robots together carry the watering cans away.

The third task was ".

Blue

reeling movement allowed the rope to bring the three watering cans' handles below, then tightening the rope, the two robots then used their leg joints to lift their bodies, and the taut rope would The third task is.

Leaving one robot on the upper platform as an anchor point, Blue along the Red come together, maintaining the state of the watering cans being lifted, and finally, the two robots worked together to carry away the watering cans.

the third task is

}}.

the rope is released at a speed roughly matching the vehicle speed. Upon reaching the bottom of the slope, Red the rope is released at a speed roughly matching the vehicle speed. Upon reaching the bottom of the slope, Blue the rope is released at a speed roughly matching the vehicle speed. Upon reaching the bottom of the slope, 49° the rope is released at a speed roughly matching the vehicle speed. Upon reaching the bottom of the slope, the rope is released at a speed roughly matching the vehicle speed. Upon reaching the bottom of the slope, Blue Use legs to hold the plush dog, then climb up the slope. During the process, alternate between using the rope to climb and adjusting the body angle with the wheels, trying to keep the body level as much as possible to prevent the plush dog from falling down.

The team did a calculation using a simplified quasi-static force analysis:

Blue

Weight

9.4kg

49°

The component of the weight along the slope is approximately 69.6N.

1.15

Without the help of the rope, relying only on the wheels for traction, the equivalent friction coefficient must be at least approximately 55.1N.

The average estimated tension of the rope during the climbing phase is 79%,.

14.5N

This accounts for approximately

of the weight component, with the remaining approximately 0.24.

03.

being supported by the wheels, corresponding to an equivalent friction coefficient reduced to approximately

The rope has become part of the robot's body.

TwinX

Researchers believe that in

the separated state itself is a functional state, no longer just a transitional stage in the reconfiguration process. The abilities of four legs, steering wheels, and mobility are capabilities after the merging, while the actions of carrying, hooking, and pulling come from the relationship between the two separate but connected robots.

This rope also brings a kind of design freedom different from rigid linkages and joints.:

While the two robots remain connected, the distance, relative position, and tension can all vary, allowing the body to be in a state other than

a completely rigid merged state

and the

or completely independent

Two extremes, and the intermediate distributed configuration.

The team's next plan is to expand to systems with more robots and more ropes., The research will study state switching according to task planning, and introduce direct measurement of tension and closed-loop control, for more continuous regulation of the mechanical relationship between the two bodies.

Paper chain

link:

https://doi.org/10.1002/aisy.70559

END

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A Reconfigurable Robotic System Using an Interbody Wire for Merging and Cooperative Tasks

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