Modular Soft Robots (MSRs)
Suggested Readings
[2020, Review] Modular Soft Robotics: Modular Units, Connection Mechanisms, and Applications (pdf)
[2007] Modular Self-Reconfigurable Robot Systems. Challenges and Opportunities for the Future
[2020, Thesis] A New Paradigm in Reconfigurable Robotics
[2012, Review] A Modular Approach to Soft Robots (Onal, Rus)
Nonlinear Modeling and Docking Tests of a Soft Modular Robot
Vacuum‐Powered Soft Pneumatic Twisting Actuators to Empower New Capabilities for Soft Robots
Modular assembly of soft deployable structures and robots
[Vacuubes] A Vacuum-Based Bonding Mechanism for Modular Robotics
Additional:
https://www.wikiwand.com/en/Self-reconfiguring_modular_robot#
Overview of Modular Soft Robots
Pros
+ Versatility
+ Robustness - modular upgrades & repairs
+ Low cost for manufacturing & maintenance
+ Adaptability to changing task & environments
+ Ease of repair by changing only damaged modules
+ Ease of transport & storage (e.g Space Launches)
+ Scalable
+ A small set of modules can enable infinite morphologies
Cons
- Complex and time-consuming to design
- Higher cost than application-specific soft robots
- Still in their infancy
- Couplings are most critical
- Couplings require custom design
- Choice of couplings still very limited.
- More complex to control than app-specific SRs
- Performance tradeoffs compared to nonmodular
Ful list of Pros & Cons of modular designs in the Modularity Resource Guide.
Capabilities
- Adaptation to new Tasks and Environments
- Self Assembly
- Self Repair
- Reconfigurability
- Reusability of modules
- Fit into confined spaces
- High packing density when disassembled
Applications
- Medical, Surgical, Implantable
- Home assistance (a modular chain manipulator)
- Physical representation of virtual objects
- Temporary housing structures beyond earth
- Terrain exploration
- Search and Rescue
- Minimally invasive surgery
- Safe human-robot interaction
Levels of Configurability
Configurable [48-67]
The parts are designed for a specific configuration or application
![[msr] modular gripper.png](https://static.wixstatic.com/media/cefaa7_7c685a913232458ea11e5af6dc575bc6~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20modular%20gripper.png)
![[msr] Jellifish Robot.png](https://static.wixstatic.com/media/cefaa7_ec4f5bbc7e864f1f967708233749127d~mv2.png/v1/fill/w_198,h_159,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20Jellifish%20Robot.png)
![[msr] implantable.png](https://static.wixstatic.com/media/cefaa7_345a03f59d014fa1ad2915800a879d20~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20implantable.png)
![[msr] modular sleeve.gif](https://static.wixstatic.com/media/cefaa7_bc33f167afc745a9b50c1829077033ee~mv2.gif)
![[msr] surgical manipulator.png](https://static.wixstatic.com/media/cefaa7_59921c65d9c2447eb13234054addec43~mv2.png/v1/fill/w_200,h_160,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20surgical%20manipulator.png)
![[msr] Soft Robotic Snake.png](https://static.wixstatic.com/media/cefaa7_2c5894f90976416183c22166ecc14a28~mv2.png/v1/fill/w_200,h_160,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20Soft%20Robotic%20Snake.png)
![[msr] wormbot.png](https://static.wixstatic.com/media/cefaa7_7ff3a781c8b24e108dc097b14ef3d569~mv2.png/v1/fill/w_198,h_159,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20wormbot.png)
Reconfigurable [47,68-87]
Capable of repeated structural or functional transformations.
Consist of homogeneous or heterogeneous units
![[msr] CMMWorm.png](https://static.wixstatic.com/media/cefaa7_8e5ff7df2a314cce9b8ffa8e9d41e5ad~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20CMMWorm.png)
![[msr] V-SPA.png](https://static.wixstatic.com/media/cefaa7_ec8e551e679e4adfbfcd4c6f55da3a30~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20V-SPA.png)
![[msr] SoBL.png](https://static.wixstatic.com/media/cefaa7_c83dfe3a64a14007b1f888cf99885c36~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20SoBL.png)
![[msr] morphIO.png](https://static.wixstatic.com/media/cefaa7_e61248afa82e404db0b1764d436cda34~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20morphIO.png)
![[msr] Reconfigurable.png](https://static.wixstatic.com/media/cefaa7_5549a269093848a5873dc9c01c19e31d~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20Reconfigurable.png)
![[msr] Modular Approch.png](https://static.wixstatic.com/media/cefaa7_e3d0ac216c6f439381c61fcb54670bdf~mv2.png/v1/fill/w_228,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20Modular%20Approch.png)
![[msr] DeployBot.gif](https://static.wixstatic.com/media/cefaa7_a9d96cc49eee4b87915259a9df8eaf26~mv2.gif)
![[msr] inflatibits.png](https://static.wixstatic.com/media/cefaa7_76ae52ea850140d781cb776f9210b72a~mv2.png/v1/fill/w_198,h_159,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20inflatibits.png)
![[msr] soft lego.png](https://static.wixstatic.com/media/cefaa7_9ac7cfe383c549c397798f6fadf93ce1~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20soft%20lego.png)
![[msr] Click-e-Bricks.png](https://static.wixstatic.com/media/cefaa7_3920b43b15834650945ca6f4f7571bd0~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20Click-e-Bricks.png)
![[msr] Elastomeric Tiles.png](https://static.wixstatic.com/media/cefaa7_917a36881ca2498b9dc65547008d5f4a~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20Elastomeric%20Tiles.png)
![[msr] starfish.png](https://static.wixstatic.com/media/cefaa7_22a8b783c820491d98852eccf11904a0~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20starfish.png)
![[msr] Arthrobots.jpeg](https://static.wixstatic.com/media/cefaa7_e1bf91673c8f43eaa030c5b8fc2a1556~mv2.jpeg/v1/fill/w_198,h_158,al_c,q_80,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20Arthrobots.jpeg)
Self-Reconfigurable [88,89]
Capable to achieving various morphologies automatically.
![[Modular Soft Robotics] Omnidirectional](https://static.wixstatic.com/media/cefaa7_6098f5d21e624359a7a310b6aeed9580~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5BModular%20Soft%20Robotics%5D%20Omnidirectional%20.png)
![[msr] SoftCubes.png](https://static.wixstatic.com/media/cefaa7_4873f9227e6a4ccfae98cf2a43831c7c~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%20SoftCubes.png)
Architecture Types
Reconfigurable robots are classified into three types by the geometric arrangements of their units, Some are hybrids.
Mobile Architecture
The individual modules are mobile and can attach individually
+ Modules can be physically disconnected but operate
as a single unit together.
+ Enables applications like self assembly and swarms.
- Modules are complex and expensive
Lattice Architecture
Modules are arranged and connected in some regular, 2D or 3D pattern, such as a simple cubic or hexagonal grid
+ Control & Motion can be executed in parallel
+ Easily scaled
- Movies can only be at discrete locations on the lattice
Chain Architecture
The modules connect to each other as a chain topology. The underlying structure is serial.
+ Folding is possible
+ Versatile in locomotion patterns
+ Connectable in 2D or 3D patterns
- Computationally demanding
- Difficult to control
Coupling Mechanisms & Interconnects
The connection mechanism between modules is the most critical part for modular systems with physically-connected modules. They determines factors such as range of motion, capabilities, efficiency, and overall size of a modular robot. A variety of connection types are possible between modules, each with its oen pros and cons, and there is not one best solution.
-
Desirable Properties
-
Small Size
-
High Mechanical Strength under all loading scenarios
-
Information Transmission Capability
-
Power Transmission Capability
-
Reversibility & Repeatability
-
Ease & Speed of connection / disconnection
-
Self-Alignment
-
Very low or no power consumption
-
Orientation invariance & Genderlessness
-
Unilateral instead of bilateral actuation
-
Compliant rather than rigid
-
Low cost
-
Mechanical
Pros
+ Most common with high diversity
+ High reliability
+ Alignment precision
+ Self-alignment possible
+ High connection strength
Cons
- Typically large and bulky
- Difficult to detach
Rigid
![[connector] Modular Robotic Wrist.png](https://static.wixstatic.com/media/cefaa7_f583b411dd8d4d6ea977756bd9640913~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20Modular%20Robotic%20Wrist.png)
![[connector] Legris + 3D print.png](https://static.wixstatic.com/media/cefaa7_3ba15e6cce804fd0bc995ccb0b7279a5~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20Legris%20%2B%203D%20print.png)
![[connector] snap-lock.png](https://static.wixstatic.com/media/cefaa7_7cfa54d7454648f6a04041f92aaefdf5~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20snap-lock.png)
![[connector] v-spa.png](https://static.wixstatic.com/media/cefaa7_50140a61776646dbb1e5ea571d1bba34~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20v-spa.png)
![[connector] screws & spacers.png](https://static.wixstatic.com/media/cefaa7_8892e2acd92248f59fcc8c0a3abfb586~mv2.png/v1/fill/w_200,h_160,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20screws%20%26%20spacers.png)
Soft
+ Maintain compliance of the soft robot
- Can't withstand high pressures or forces
- Virtually no examples in the literature
- Fully custom made
![[connector] soft bystable.png](https://static.wixstatic.com/media/cefaa7_fa19c65fd55d482d983656a187a12400~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20soft%20bystable.png)
Bystable
Magnetic
Pros
+ Easy attachment
+ Easy manual detashment
+ Self aligning
+ Conductive
+ Genderless & Orientation Invariant
Cons
- Reduce compliance of robot
Permanent Magnets
+ No power required
+ Very compact
+ Attachment to/of other metal parts possible
+ Easily combined with other actuators (Motors, SMA)
+ Suitable for submerged applications
- Disconnect requires extra actuation
- Misalignment or disconnection under load
![[connector] Magnet with hole.png](https://static.wixstatic.com/media/cefaa7_c7109f67d92e4540b9d5b19dd14ca4d8~mv2.png/v1/fill/w_200,h_160,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20Magnet%20with%20hole.png)
Magnet with hole
![[connector] magnet.png](https://static.wixstatic.com/media/cefaa7_d6707f5aba4c405ca5827e4f611fd76d~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20magnet.png)
![[connector] Soft Modular Robotic Cubes.p](https://static.wixstatic.com/media/cefaa7_fb5567ba559b4f18b69655bdeb91058b~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20Soft%20Modular%20Robotic%20Cubes_p.png)
![[connector] Caterpillar.png](https://static.wixstatic.com/media/cefaa7_7b30b11d30374a2b8344ce0ee302928c~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20Caterpillar.png)
![[connector] magnet.png](https://static.wixstatic.com/media/cefaa7_4c122329673b4dd29518f4bfccf4b6e8~mv2.png/v1/fill/w_200,h_160,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20magnet.png)
Multiple Magnets
Placeholder
Placeholder
Placeholder
Electromagnets
+ Auto Connect & Disconnect possible
- Continuous power consumption during hold
- Sufficient space required
Electropermanent Magnet
+ Low power; used only for state change
+ Maintain state without power
- Expensive
- Custom fabrication required
Adhesive
Pros
+ Minimum spacing requirements
+ High connection strength
+ Low complexity
+ Genderless & orientation invariant
Cons
- slow connection & disconnection
- accurate alignment needed
Self-soldering
+ Low melt point at 62°C for Field's Alloy
+ Easily manufacturable by PCB fabricators
+ Small & Lightweight (2g, 3mm thick)
+ Programmable / Reversable
+ Conductive
- Not compliant, but can be made with flex PCBs
- Unsuitable for underwater applications
- Slow - 10s heating; 30s cooling
- Prone to corrosion
- Low durability (100+ cycles before failure)
Self-Soldering
Active Freeze (via peltier devices)
+ Low melt point at 62°C for Field's Alloy
+ Easily manufacturable by PCB fabricators
+ Small & Lightweight (2g, 3mm thick)
+ Programmable / Reversable
+ Conductive
- Not compliant, but can be made with flex PCBs
- Unsuitable for underwater applications
- Slow - 10s heating; 30s cooling
- Prone to corrosion
- Low durability (100+ cycles before failure)
Hot-melt Adhesives / hot glue (HMAs) [135]
+ Connection & Disconnection possible
+ Nonsticky, viscoelastic solid at 25◦C
+ Heating/Cooling can be done locally or globally
- Slow
- Heating Mechanism required
- HMA Applica
- Cooling through natural heat dissipation, but active cooling is possible.
-
At room temperature (Tr around 25◦C), the material is an viscoelastic solid with no adhesiveness, thus unable to form new bonds. But existing connections are maintained with high bonding strength.
-
At softening-point temperatures Ts, the material starts to become visco-plastic and adhesive. The bond is drastically weakened, and maintain an established connection becomes difficult.
-
At melting point temperature Tm (generally 150◦C), the the material transforms into a low-viscosity fluid.
NOTE: Ts and Tm vary depending on the ingredients of HMAs, and they are generally temperature ranges.
Electrostatic Adhesion [136]
+ Connection & Disconnection possible
- High voltage required
Glue / Silicone / Tape
+ Leakproof
+ No additional structures needed
+ Easy to apply
+ Dovetail joints can increase bonding area
[83]
- Difficult or impossible to disconnect
- Compliance is maintained
- Bonding strength proportional to bonded area
![[connector] glued.png](https://static.wixstatic.com/media/cefaa7_8b92171ee1604b969fb167b8463c7673~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20glued.png)
Silicone Adhesion
![[msr] 2D manipulator.png](https://static.wixstatic.com/media/cefaa7_a1c302abea48480f92adb12bfc7cac59~mv2.png/v1/fill/w_198,h_158,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bmsr%5D%202D%20manipulator.png)
![[connector] Dovetail Joints.png](https://static.wixstatic.com/media/cefaa7_85c510b1eb9f40a69c14f95148962133~mv2.png/v1/fill/w_198,h_159,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20Dovetail%20Joints.png)
Dovetail Joints
![[connector] Arthrobots.png](https://static.wixstatic.com/media/cefaa7_d288ad3d332a44e6ae4f03f2e8ebc701~mv2.png/v1/fill/w_198,h_159,al_c,q_85,usm_0.66_1.00_0.01,blur_3,enc_auto/%5Bconnector%5D%20Arthrobots.png)
Arthrobots
Pneumatic (Vacuum)
Pros
+ Easy connection and disconnection
+ Automatic alignment possible
+ High connection strength
+ Low complexity
+ Can use the robot's pneumatic driver
Cons
- accurate alignment needed for good connection
- some designs prone to misalignment
- extra pump may be required
- nonconductive
Vacuubes
