Safety-focused obstacle-crossing system for FAÇADE-cleaning robots

Abstract

The present invention relates to a façade-cleaning robot with an integrated, safety- focused obstacle-crossing system. The system utilizes at least six wheels and two non-contact suction cups with flexible skirts to navigate small obstacles and gaps on vertical or near-vertical surfaces. A cam-based mechanism, driven by one or two actuators, precisely controls the sequential lifting and lowering of the wheels, ensuring at least four wheels maintain surface contact for stability. The flexible skirts on the suction cups minimize suction loss as they deform around obstacles. This enables the robot to continue its cleaning operation without interruption while crossing obstacles. The system is lightweight, energy-efficient, and designed to minimize moment loads by maintaining a level chassis. Furthermore, the components serve dual functions, providing inherent redundancy and resistance to catastrophic failure, thereby enhancing the robot's reliability and operational safety.

Description

SAFETY-FOCUSED OBSTACLE-CROSSING SYSTEM FOR FA ADE-CLEANING ROBOTSRELATED PATENT APPLICATION

[0001] This application claims the priority to and benefit of Indian Provisional Patent Application No. 202441071852 filed on September 23, 2024; the disclosures of which are incorporated herein by reference.TECHNICAL FIELD

[0002] The present invention relates to the technical field of robotics, and more specifically, to systems and methods for enabling an autonomous robot to traverse vertical or near-vertical surfaces. In particular, the invention provides an obstacle-crossing system for a facade-cleaning robot that maintains operational consistency and cleaning pressure while navigating minor surface discontinuities, gaps, or protrusions on a building exterior.BACKGROUND

[0003] Facade-cleaning robots are the future for cleaning high-rise buildings and large surfaces that are otherwise inaccessible or unsafe for human workers. However, existing robots in this field face limitations when it comes to crossing obstacles, such as ridges or joints in building facades.

[0004] A perfect cleaning robot requires good cleaning quality with high speed, low weight and low cost. To achieve good cleaning quality the robot must provide steady motion speed to its cleaning apparatus. This eliminates walking like mechanisms for climbing like Chinese patent CN 119218331A.

[0005] For smooth movement a wheel or track based motion system does well but these motion systems can only work with dragged seal suction cups (as used by US7520356B2) or with non-contact suction cups (like US20230037818A1).

[0006] Wheeled motion system are usually unable to traverse large obstacles. Designs like CN211107764U attack the problem by legged systems but they have difficulty achieving steady motion and require very large quantity of motors that also need very large output torque in order to resist the gravitational forces continuously. Prior art CN115778221B tries to solve the problem by making each leg have wheel and a suction cup but this still needs several motors and several high performance dragged seal suction cups. Further smaller suction cups have lower efficiency and need disproportionately higher suction pressure.

[0007] Ideal solution to above problems would be a system that uses just 1 actuator to achieve obstacle crossing while using a minimum number of large suction cups. Since a robot must have a minimum 2 suction cups for redundancy, an ideal system must use one actuator along with 2 suction cups and a minimum wheel count to achieve obstacle crossing. Further this system must also be capable of cleaning the glass while its crossing the obstacle to enable thorough cleaning without leaving unclean regions.

[0008] The obstacle crossing system must also ensure low moment loads during crossing of obstacles. These loads mandate extra suction force to avoid toppling off the vertical facade due to gravitational forces. Prior art like CN 111358329B suffer from these problems as during obstacle crossing they move entire sections of the robot away from the glass.

[0009] Chinese patent CN 119218331A uses a mechanical arm to connect 2 contact seal type suction cups that help attach to the glass and go over obstacles. While this may provide ability to cross large obstacles, the center of mass of the robot sits very far from the suction cups hence requiring excess suction to balance the moment of gravity. The motion is also not smooth as it is a intermittent walking like motion that is unsuitable to a high productivity cleaning mechanism.

[0010] Hence, there is a need to develop a facade-cleaning robot that overcomes the limitations of the prior art. Known prior arts struggle to maintain consistent cleaning while navigating obstacles, leading to inefficiencies and increased energy consumptionOBJECTIVES

[0011] A primary object of the present invention is to provide a lightweight and efficient obstacle-crossing system for facade-cleaning robots.

[0012] Another object of the present invention is to provide a system that allows facade-cleaning robots to maintain cleaning pressure and operational consistency while overcoming small obstacles, ensuring uninterrupted cleaned areas. In other words the system can clean and cross obstacles simultaneously.

[0013] Another object of the present invention is to provide a system that facilitates obstacle crossing without the need for heavy or high-torque motors, thereby reducing the overall weight and energy consumption of the robot.

[0014] Another objective of the invention is to allow crossing of obstacles with minimum increase in center of mass distance from the glass facade to minimize moment loads and hence minimize additional suction needed.

[0015] Another object of the present invention is to minimize the number of additional components required for obstacle crossing, ensuring that any added parts also serve multiple functions, such as contributing to the redundancy system for emergencies or system failures.

[0016] Another object of the present invention is to provide a facadecleaning robot that can continue to function effectively even in the presence of obstacles, using components that serve dual purposes for both obstacle crossing and redundancy.

[0017] Another object of the present invention is to provide a facade cleaning robot that can provide constant speed motion during cleaning to maximize cleaning system efficacy.

[0018] Another objective is to ensure minimum number of motors while achieving obstacle crossing action.

[0019] Another objective is to design an obstacle crossing system that can work with large non-contact suction cups.

[0020] Another objective is to design an obstacle crossing system that can effectively cross gaps in the glass facade.

[0021] Another objective is to design a safety focused design where if the obstacle crossing motor breaks down it doesn’t result in an invalid configuration of the robot.SUMMARY

[0022] The present invention discloses an obstacle-crossing system for a robot configured to traverse a vertical or near-vertical surface. The system comprises a chassis, at least six wheels movably coupled to the chassis and arranged in at least two pairs of three, and at least two non-contact suction cups, each equipped with a flexible skirt. The system further comprises atleast one actuator coupled to a lifting mechanism, which is configured to sequentially lift and lower a selected pair of said wheels to enable the robot to traverse an obstacle. This lifting mechanism maintains surface contact with at least four of the wheels while the flexible skirts on the suction cups deform around the obstacle to minimize suction pressure loss. The system is designed to enable the robot to continue its cleaning operation without interruption while crossing obstacles, significantly improving efficiency. The present invention is also characterized by its low moment loads, reduced motor torque requirements, and inherent safety features, as the lifting mechanism resists catastrophic failure states.BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG.l illustrates the robot as it crosses an obstacle.

[0024] FIG.2 illustrates the obstacle-crossing system used by the robot in isometric view. The embodiment shown has a single motor driving both CAM shafts enabling obstacle crossing using only one actuator.

[0025] FIG.3 illustrates the embodiment that uses two motors to drive the two CAM shafts improving capability over obstacles that approach at oblique angles to the robot.

[0026] FIG.4 illustrates another embodiment with a different type of CAM design which enables same functionality. This CAM uses a sliding CAM shaft instead of one that rotates.

[0027] [1] is Lifting mechanism motor.[2] is driveshaft to drive multiple CAMs[3] is CAM shaft.[4] is a CAM.[5] is the suction cup.[6] is the suction cup skirt.[7] is the front wheel(s)[8] is the middle wheel(s).[9] is the rear wheel(s).

[0010] is the chassis.

[0011] is the cleaning system.

[0012] is a steering motor for enabling holonomic drive.DETAILED DESCRIPTION

[0028] The present invention provides a safety-focused obstacle-crossing system integrated into a facade-cleaning robot. In a first exemplary embodiment, as depicted in Figure 2, the robot comprises a main chassis

[0010] to which all primary components are mounted, including a cleaning system

[0011] , power source, and control electronics. The mobility system consists of six driven wheels — two front wheels [7], two middle wheels [8],and two rear wheels [9] — arranged in a three-by-two configuration. The vertical position of these wheels is controlled by a lifting mechanism comprising two separate camshafts [3], one for each side of the robot. Each camshaft is driven by a driveshaft (2) driven by a dedicated motor [1] and contains three cams [4] that are precisely timed to sequentially lift and lower the front, middle, and rear wheels as the robot advances. This cam-based mechanism ensures a smooth transition over obstacles while maintaining constant contact with the facade through at least four wheels at any given time, thereby ensuring stability. The cam timing is critical to the operation, being configured to fully engage a wheel before the lifting process of another wheel commences. The robot adheres to the vertical surface using two or more large, non-contact suction cups [5]. A key feature of these suction cups is the flexible skirt [6], which is designed to deform and encapsulate an obstacle, thereby minimizing the loss of suction pressure as the robot crosses it. This allows the robot to maintain its adherence to the surface and continue its cleaning operation without interruption.

[0029] Figure 1 shows the robot as it crosses an obstacle. The drawing shows 7 steps.1. Robot approaches the obstacle cleaning right to the edge of the obstacle.2. Robot picks the cleaning system and places it in front of the obstacle.3. Robot starts cleaning on the other side of the obstacle.4. Robot picks the front wheels up and engages middle wheels. Since non- contact skirt-based suction cups can create suction even with the obstacle under them, suction is created by both suction cups. However front suction cup may be made to make less suction as front wheel is lifted.5. Front wheel is engaged, and Middle wheel is lifted. Robot moves forward and the skirt encapsulates obstacle to minimize leakage.6. Rear wheel is lifted when the object is close to it and middle wheel is engaged to maintain balance.7. System enters initial state i.e., rear and front wheel engaged, and middle wheel lifted, once obstacle is behind the rear wheel.

[0030] In a second, more practical embodiment, the system utilizes two separate motors [1] to drive the left and right camshafts independently. This configuration offers enhanced flexibility, allowing for differential timing of the wheel lifting process on either side of the robot. This is particularly advantageous when the robot encounters an obstacle that is not perfectly parallel to its direction of motion, enabling a more adaptive and efficient traversal. For general facade navigation, the robot can operate in a four- wheeled holonomic drive mode, where the middle wheels [2] are intentionally maintained in a lifted state. This provides maximum manoeuvrability across the surface without the need to give steering motors

[0012] to the middle wheels . The system is designed such that the obstaclecrossing mechanism requires motor power only during configuration changes (i.e., when lifting or lowering a wheel), with no continuous load on the motors to maintain a static configuration. The chassis

[0010] remains level throughout the obstacle-crossing process, which prevents the center of mass from shifting significantly away from the facade, thereby minimizing the gravitational moment loads and the need for high-pressure suction to counteract them. The cleaning system

[0011] remains engaged and operational throughout the process, ensuring no areas adjacent to the obstacle are missed.

[0031] An alternate embodiment is shown in FIG. 4 which uses a different CAM system that uses sliding CAM design instead of a rotating CAM shaft as shown in embodiments shown in FIG. 2 and FIG. 3.

[0032] A crucial aspect of the invention is its inherent redundancy and safety. The use of six wheels provides redundancy; in the event of a failure of a single wheel's motor or mechanism, the remaining wheels can still provide sufficient support for the robot to return to a safe location. Similarly, the suction cups not only provide adherence but also act as a failsafe system. Furthermore, the cam-based lifting mechanism is intrinsically safe. Because the physical shape of the cam encodes the wheel's position, there is no configuration in which all six wheels could be lifted simultaneously due to a control or motor failure, thereby preventing catastrophic dislodgement.

[0033] The invention is not limited to facade cleaning but is also applicable to other industrial uses, such as inspection robots for vertical surfaces, particularly those with rough textures where non-contact suction cups are most effective. The manufacturing process involves the integration of the camshafts and motors with the chassis and wheels, followed by the attachment of the suction cups and the cleaning apparatus.ADVANTAGES

[0034] The invention provides several technical and commercial advantages over the prior art. The use of a lightweight cam-based lifting mechanism significantly reduces the robot's overall weight and energy consumption by eliminating the need for heavy, high-torque motors or gearboxes. This leads to a more efficient and cost-effective system. The ability to maintain continuous cleaning operations while traversingobstacles ensures a higher cleaning quality and greater operational productivity compared to systems that must pause or re-configure. The safety-focused design, which includes component redundancy and a mechanism that resists catastrophic failure, enhances the robot's reliability, and reduces the risk of expensive damage or failure. By minimizing the moment loads during obstacle negotiation, the invention also reduces the required suction force, further contributing to energy savings. The simplicity of the design, with a low part count and dual-purpose components, simplifies manufacturing and maintenance processes, leading to a lower total cost of ownership.

Claims

We claim:

1. An obstacle-crossing system for a robot configured to traverse a vertical or near- vertical surface, comprising:I. a chassis [10];II. at least six wheels [7,8,9] movably coupled to the chassis, said wheels being arranged in at least three pairs, wherein each pair is selectively engageable with the surface;III. at least two non-contact suction cups [5] coupled to the chassis, each suction cup comprising a flexible skirt; andIV. at least one actuator [1] coupled to a lifting mechanism [3,4], said lifting mechanism configured to sequentially lift and lower a selected pair of said wheels to enable said robot to traverse an obstacle on said surface, while maintaining surface contact with at least four of said wheels and while said flexible skirts deform around said obstacle to minimize a loss of suction pressure.

2. The system of claim 1, wherein said lifting mechanism comprises a pair of camshafts [3], each camshaft configured to control the lifting and lowering of a set of wheels on one side of said chassis.

3. The system of claim 2, wherein each camshaft comprises a plurality of cams [4], each cam being precisely timed to encode the vertical motion of a corresponding wheel.

4. The system of claim 2, where each of the two camshafts has its own separate motor, allowing the robot to lift and lower the wheels on each side independently.

5. The system of claim 1, wherein said robot is a facade-cleaning robot, and wherein a cleaning system [11] is configured to remain operational and in contact with said surface while said robot traverses said obstacle.

6. The system of claim 1, wherein said system is configured to maintain a constant chassis [10] level during obstacle traversal, thereby minimising effect on cleaning and suction systems.

7. The system of claim 1, wherein said wheels [7,8,9] and said suction cups [5] are configured to serve as redundant components to provide a failsafe mechanism in the event of a component failure.

8. A method for traversing an obstacle on a vertical or near-vertical surface with a robotic device, said method comprising the steps of:I. adhering said robotic device to said surface using at least two noncontact suction cups [5], each having a flexible skirt;II. moving said robotic device towards an obstacle using at least four wheels [7,8,9] in contact with said surface;III. engaging a lifting mechanism [3,4] to sequentially lift and lower one pair of said wheels to enable said robotic device to traverse said obstacle;IV. deforming said flexible skirts around said obstacle to maintain suction pressure; andV. maintaining at least four wheels in contact with said surface at all times during said obstacle traversal.

9. The method of claim 8, wherein said lifting mechanism is a cam-based system driven by at least one actuator [1].

10. The method of claim 8, wherein said robotic device continues to perform a cleaning operation while traversing said obstacle.

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