Surface treatment device, surface treatment system, surface treatment method

Abstract

The invention relates to a surface treatment device (1) comprising a tool head (2) with a shape-adaptive portion (3) for contacting a workpiece (4), wherein said shape-adaptive portion (3) is configured to conform to a surface of the workpiece (4) by plastic or elastic deformation, wherein the surface treatment device (1) comprises one or more sensors (6,14,60) configured to record a signal from the tool head (2) indicative of a state of the tool head (2), a state of the workpiece (4) and / or an interaction between the tool head (2) and the workpiece (4) and to generate sensor data from the recorded signal. The invention further relates to a surfaces treatment system (10), a surface treatment method and a computer program.

Description

[0001] The present invention relates to a surface treatment device, a surface treatment system, a surface treatment method and a computer program.

[0002] In the field of machining and material processing, tool heads are critical components that directly engage with workpieces to perform shaping, grinding, or other operations. The interaction between the tool head and the workpiece inherently involves high mechanical stresses, friction, and thermal loads. These conditions inevitably lead to wear and degradation of both the tool head and the workpiece surface. Wear of the tool head can result in diminished precision, reduced efficiency, and the need for frequent maintenance or replacement. At the same time, improper interaction or excessive wear may adversely affect the surface quality of the workpiece, causing defects, dimensional inaccuracies, or material damage. The dynamic interplay between tool head durability and workpiece integrity presents a central challenge in achieving consistent machining performance, extending the service life of components, and ensuring the economic viability of production processes.

[0003] Based on this, it is a subject of the present invention to provide a surface treatment device, a surface treatment system and a surface treatment method that enable efficient surface treatment of various workpieces with different, complex geometries with a single device and monitoring of a state of the tool head, a state of the workpiece and / or an interaction between the tool head and the workpiece.

[0004] This task is solved by a surface treatment device with the features of claim 1, a surface treatment system according to claim 13 and a surface treatment method according to claim 15.

[0005] Advantageous embodiments of the invention are given in the corresponding dependent claims and described in the following.

[0006] A first aspect of the invention relates to a surface treatment device comprising a tool head with a shape-adaptive portion for contacting a workpiece, wherein said shape-adaptive portion is configured to conform to a surface of the workpiece by plastic or elastic deformation, wherein the surface treatment device comprises one or more sensors configured to record a signal from the tool head indicative of a state of the tool head, a state of the workpiece and / or an interaction between the tool head and the workpiece and to generate sensor data from the recorded signal.

[0007] As an advantageous consequence of the plastically or elastically deformable shape-adaptive portion of the tool head, one and the same tool head can be used for various workpieces with different, complex surface geometries.

[0008] In the context of the present invention, the terms "plastic deformation" and "elastic deformation" are distinguished as follows: A plastic deformation may remain after a force applied to the shape-adaptive portion, which may particularly be caused by a contact between the tool head and a workpiece, is removed. Hence, a plastically deformable shape-adaptive portion can maintain its deformed shape even if the tool head and the workpiece are moved away from each other after contact. For example, a plastically deformable shape-adaptive portion can be realized by means of a shape-adaptive portion comprising a volume filled with solid particles as disclosed herein. In contrast, an elastic deformation may reverse, once a force applied to the shape-adaptive portion is removed. Hence, an elastically deformable shape-adaptive portion can reverse the deformation caused by the contact with the workpiece once the tool head and the workpiece are moved away from each other after contact. For example, the shape-adaptive portion comprises an elastic foam or it can least partially enclose a closed volume filled with a gas, such that the shape-adaptive portion can deform elastically under a reversible compression of the foam or the gas inside the shape-adaptive portion for conforming to the surface of a workpiece.

[0009] In an embodiment of the invention, the one or more sensors comprises at least one an active sensor, the active sensor comprising: an emitter unit configured to emit an emitter signal, such that the emitter signal can be modulated by an interaction with the tool head, the workpiece and / or by an interaction between the tool head and the workpiece, thereby forming said signal, and a detector unit configured to record the signal.

[0010] The active sound sensor has for example the technical advantage that it allows to probe a morphology of the tool head and / or the workpiece by exposing the tool head and / or the workpiece to said emitter signal and detecting a modulated emitter signal, for example a reflected emitter signal reflected from the tool head and / or the workpiece, which is indicative for the morphology of the tool head and / or the workpiece. Specific examples for different active sensors based on the different emitter signals are disclosed herein.

[0011] In particular, the emitter unit is arranged and configured to emit the emitter signal into an internal space of the tool head, wherein the internal space is delimited from the workpiece by the shape-adaptive portion, when the shape-adaptive portion conforms to the surface of the workpiece, such that the signal can be formed in the internal space of the tool head, and wherein the detector unit is arranged and configured to record the signal formed in the internal space of the tool head. As such, the active sensor can determine the state of the tool head while being in contact with the workpiece. This is advantageous compared to sensors focusing on the outer surface of the tool head, particularly its contact portion, which is typically covered during surface treatment as it is in contact with the workpiece, preventing in-situ determination of the state of the tool head. At the same time, the emitter signal is in this embodiment at least partially shielded from the surrounding via the shape-adaptive portion of the tool head and / or other structures delimiting the tool head from its surrounding, which enables an efficient probing particularly of the state of the tool head at low noise due to environmental influences.

[0012] According to an embodiment of the invention, the tool head comprises a deformable shell arranged on or forming an outer surface of the shape-adaptive portion, wherein the tool head is configured to adopt a first state in which the shape-adaptive portion of the tool head and thus a contact portion of the deformable shell is rendered flexible so as to conform to the surface of the workpiece, and a second state in which the shape-adaptive portion of the tool head and thus the contact portion of the deformable shell is stiff and maintains its outer contour. The deformable shell can thus form an outer surface of the shape-adaptive portion and thus be integrally connected with it or it may alternatively be arranged on an outside of the shape-adaptive portion, in the sense of an outer layer. In particular, in the latter case the deformable shell can be repeatably attachable or detachable from the shape-adaptive portion, such that the deformable shell can be exchanged in case of wear caused by an interaction between the tool head and the workpiece mediated by the deformable shell.

[0013] In another embodiment of the invention, the surface treatment device comprises a stiffness control unit configured to change a stiffness of the shape-adaptive portion of the tool head to and between a first stiffness associated with the first state and a second stiffness associated with the second state. In particular, the stiffness control unit can change the stiffness of the shape-adaptive portion by controlling a process parameter that affects the stiffness of the shape-adaptive portion. For example, the process parameter may be a gas pressure or a temperature inside the shape-adaptive portion.

[0014] In an embodiment of the invention, the deformable shell comprises an abrasive-, polishing-, or capillary layer for treating the surface of the workpiece. Possible surface treatment processes with abrasive- or polishing layers include sanding, grinding and polishing, wherein a capillary layer particularly allows additive surface processing like painting or waxing. The capillary layer can hold an additive substance in a liquid or powder form that can be refilled by dipping the tool head into the liquid or powder.

[0015] According to another embodiment of the invention, the deformable shell encloses a volume filled with solid particles. In particular, solid particles can be arranged in the form of granulate, powder or gravel. In terms of materials, the solid particles can for example be formed from one or more of the following materials: plastic, glass, ceramic, metal, sand, gravel. With respect to their size, individual solid particles may comprise diameters in the millimeter range, i.e. one millimeter or larger. Hence, individual particles may also be on the order of centimeters, decimeters, meters or more. In a specific example, the solid particles can comprise sizes between 63 micrometer and 5 centimeters.

[0016] In particular, the tool head comprises a deformable shell arranged on or forming an outer surface of the shape-adaptive portion, wherein the tool head is configured to adopt a first state in which the shape-adaptive portion of the tool head and thus a contact portion of the deformable shell is rendered flexible so as to conform to the surface of the workpiece, and a second state in which the shape-adaptive portion of the tool head and thus the contact portion of the deformable shell is stiff and maintains its outer contour, wherein the deformable shell encloses a volume filled with solid particles.

[0017] In particular, the tool head is configured to switch to the first and the second state or to transition to and between the first and the second state by adjusting a gas pressure acting on an inside of the deformable shell. For example, if the surface treatment device is used in a surrounding with atmospheric pressure conditions corresponding to a pressure of 1 atm outside the deformable shell, when the pressure drops below 1 atm, then the shell applies a force on the solid particles and the solid particles jam, acting like a solid material. The stiffness of the tool head can thus be controlled by the gas pressure inside the deformable shell.

[0018] Particularly, the surface treatment device comprises a stiffness control unit by means of a pressure adjustment unit configured to adjust the gas pressure acting on the solid particles inside the deformable shell. The pressure adjustment unit can thus switch the tool head to said first or second state so as to render the shape-adaptive portion flexible or stiff. In particular, the pressure adjustment unit can keep the tool head in said first or second state by keeping the gas pressure essentially constant, thereby realizing the conditions of a plastically deformable shape-adaptive portion that maintains its deformation even if the tool head and the workpiece are moved away from each other after contact. For example, a first gas pressure associated with the first state can be between 0.96 and 1.1 atm, particularly 1 atm and a second gas pressure associated with the second state can be between 0.5 and 0.959 atm particularly depending on properties of the solid particles used for jamming. Particularly, the solid particles can be a collection of deformable solid particles of sizes between 63 micrometer and 5 centimeter, which collection can be converted under pressure into a cohesive, partially elastic to rigid compound.

[0019] In another embodiment of the invention, the deformable shell at least partially encloses said volume filled with solid particles, wherein the deformable shell comprises an elastic layer and an abrasive-, polishing-, or capillary layer, wherein the elastic layer is arranged between the volume filled with solid particles and the abrasive-, polishing-, or capillary layer. Hence, when the solid particles jam to render the tool head stiff, the elastic layer can deform to fill spaces between individual solid particles at the interface with the deformable shell, thereby smoothing and evening out the abrasive-, polishing-, or capillary layer at the outside of the tool head. This enhances the ability of the tool head to conform to the surface of the workpiece. For example, the elastic layer comprises or consists of: polyurethane, polypropylene, neoprene and / or polyethylene.

[0020] In yet another embodiment of the invention, the tool head comprises a rigid shell arranged in an upper portion, wherein the shape-adaptive portion with its deformable shell is arranged in a lower portion of the tool head. The rigid shell thus limits the deformation and bulging to the lower portion when the tool head interacts with the surface of the workpiece and thus spatially stabilizes the shape-adaptive portion, ensuring that, during interaction with the workpiece, the shape-adaptive portion maintains controlled deformations, preventing irregular movements that could compromise the quality of the surface treatment.

[0021] For example, the state of the tool head includes a morphology of an outer surface of the tool head, particularly its contact portion, more particularly its surface roughness and / or a a gas pressure inside the shape-deformable portion or wear of an outer surface of the tool head, particularly of said deformable shell and said contact portion. The state of the workpiece can include for example a morphology, geometry, material and / or a surface structure of the workpiece. The interaction between the tool head and the workpiece can include for example a contact pressure between the tool head and the workpiece and or a relative movement between the tool head and the workpiece.

[0022] In particular, the one or more sensors comprise one or more vibration sensors configured to generate sensor data by means of vibration data from a recorded vibration signal, wherein the vibration data are indicative of vibrations caused by an interaction between the tool head and the workpiece. For example, the vibration signals result from mechanical vibrations caused by the interaction between the tool head and the workpiece. These mechanical vibrations can be detected for example by a vibration sensor attached to the tool head, particularly to its shape-adaptive portion.

[0023] In particular, the vibration sensor is an active vibration sensor, the active vibration sensor comprising: a vibration emitter unit configured to emit a vibration emitter signal, such that the vibration emitter signal can be modulated by an interaction with the tool head, the workpiece and / or by an interaction between the tool head and the workpiece, thereby forming the vibration signal, and a vibration detector unit configured to record the vibration signal.

[0024] Specifically, at least one of the one or more vibration sensors can comprise a microphone configured to generate sensor data by means of sound data from a recorded sound caused by the interaction between the tool head and the workpiece, wherein the sound data comprises the recorded sound signal and / or a spectrum of the recorded sound signal indicative of the interaction between the tool head and the workpiece. As such, the sound data encode acoustic vibrations caused by the interaction between the tool head and the workpiece.

[0025] In another embodiment of the invention, the vibration sensor is an active sound sensor, comprising: a sound emitter configured to emit a sound emitter signal, such that the sound emitter signal can be modulated by an interaction with the tool head, the workpiece and / or by an interaction between the tool head and the workpiece, thereby forming the sound signal, and said microphone.

[0026] In another embodiment of the invention, the surface treatment device comprises an active optical sensor, the active optical sensor comprising: an optical emitter configured to emit electromagnetic radiation, such that the electromagnetic radiation can be modulated by an interaction with the tool head, the workpiece and / or by an interaction between the tool head and the workpiece, thereby forming an optical signal, and an optical detector configured to record the optical signal.

[0027] Particularly, the optical emitter is arranged and configured to emit electromagnetic radiation into the internal space of the tool head, such that the optical signal can be formed in the internal space of the tool head, and wherein the optical detector is arranged and configured to record the optical signal formed in the internal space of the tool head.

[0028] For example, the optical emitter is configured to emit a geometrical pattern such as a chessboard or stripe pattern onto the tool head and / or the workpiece. The way the pattern is reflected depends on the morphology, that is, the surface geometry and -material, which modulates an image captured by the optical detector. The modulation of the image is indicative of the state of the tool head and / or the workpiece.

[0029] In another embodiment of the invention, the surface treatment device comprises an active electrical sensor, the active electrical sensor comprising: an electrical emitter unit configured to emit an electrical emitter signal, such that the electrical emitter signal can be modulated by an interaction with the tool head and / or by an interaction between the tool head and the workpiece, thereby forming an electrical signal, and an electrical detector unit configured to record the electrical signal.

[0030] Alternatively or additionally, one or more of the sensors can comprise at least one camera configured to generate sensor data by means of image data from at least one recorded image of an edge of the contact portion of the tool head.

[0031] Particularly, the surface treatment device comprises at least one pressure sensor configured to record a pressure signal indicative of an internal pressure inside the deformable shell between the solid particles and / or the contact pressure of the tool head on the workpiece and to generate sensor data by means of pressure data. For example, if the tool head comprises a deformable shell enclosing said volume filled with solid particles, at least one pressure sensor can be arranged in fluid communication with the volume. As such, a single pressure sensor is sufficient to derive both the internal pressure inside the deformable shell between the solid particles as well as the contact pressure between the tool head and the workpiece, since a contact between the tool head directly affects the internal pressure inside the deformable shell.

[0032] In particular, the surface treatment device can comprise a plurality of pressure sensors arranged and configured such that a spatial pressure distribution can be derived from the combined pressure data recorded by the plurality of pressure sensors. For example, to this end, the plurality of pressure sensors can be arranged on the contact portion of the deformable shell, such that the individual pressure sensors of the plurality of pressure sensors can record pressure data at different locations of the contact portion.

[0033] In another embodiment of the invention, the surface treatment device comprises an evaluation unit configured to determine one or more control parameters from the sensor data. In particular, the one or more control parameters comprise a contact pressure of the tool head on the workpiece and / or a relative movement between the tool head and the workpiece.

[0034] In another embodiment of the invention, the surface treatment device comprises a movement mechanism for performing a movement of the tool head with its shape-adaptive portion. For example, the tool head comprises at least one hinge for performing a translational, rotational or pivotal movement, including changes of orientation of the tool head, such that the shape-adaptive portion can be moved with respect to the workpiece, which further improves the flexibility of the surface treatment device. The movement of the surface treatment device may be further assisted by a robot according to the second aspect of the invention below.

[0035] In yet another embodiment of the invention, the surface treatment device comprises a plurality of tool heads according to the first aspect of the invention. As such, each tool head can comprise an associated shape-adaptive portion. In particular, the plurality of tool heads can be attached to and protrude from a carrier of the surface treatment device. The individual tool heads can be arranged parallel to each other along their respective longitudinal extension axes, such that a plurality of, particularly all shape-adaptive portions of the individual tool heads can conform to the surface of the workpiece at the same time. For instance, the tool heads can protrude from the platform in a configuration where the individual tool heads are arranged next to each other in a row. Alternative configurations can include tool heads arranged in multiple rows arranged next to each other. At least one, particularly all of the individual tool heads can comprise a respective movement mechanism for performing a movement of the respective tool head with its shape-adaptive portion. As such, the individual tool heads can conform locally to the surface of the workpiece with their respective shape-adaptive portion, while the tool heads can be moved independently of each other, which allows to conform multiple tool heads of the surface treatment device to multiple regions of the surface of the workpiece at the same time. This makes the surface treatment device particularly useful for sub-aperture surface treatment applications, in which the contact portion of an individual tool head is smaller than a surface to be treated.

[0036] An alternative aspect to the first aspect of the invention relates to a surface treatment device comprising a tool head with a shape-adaptive portion for contacting a workpiece, wherein said shape-adaptive portion is configured to conform to a surface of the workpiece, wherein the surface treatment device comprises one or more sensors configured to record a signal from the tool head indicative of a state of the tool head, a state of the workpiece and / or an interaction between the tool head and the workpiece and to generate sensor data from the recorded signal.

[0037] For example, the shape-adaptive portion of the tool head can conform to the surface of the workpiece by plastic or elastic deformation.

[0038] The embodiments of the first aspect of the invention can also be applied to this alternative aspect of the invention.

[0039] A second aspect of the invention relates to a surface treatment system, comprising a surface treatment device according to the first aspect of the invention or its alternative aspect, as well as a robot, wherein the surface treatment device is attached or configured to be attached to the robot, such that the surface treatment device can be moved by the robot. In the context of the present invention, the term "robot" refers to a controllable unit, capable of autonomous or semi-autonomous operation, which can carry and position the tool head of the surface treatment device according to the first aspect of the invention or its alternative aspect, allowing it particularly to move to, across and / or away from the surface of the workpiece to be treated. For example, the robot can be realized as a robotic arm that moves and controls the interaction between the tool head of the surface treatment device and the workpiece.

[0040] According to an embodiment of the invention, the surface treatment system comprises multiple surface treatment devices and one or multiple robots, wherein each surface treatment device is configured to be attached to a robot, such that each surface treatment device can be moved by its associated robot.

[0041] Particularly, if the surface treatment system comprises more than one surface treatment devices, at least one of the surface treatment devices can comprise a plurality of tool heads.

[0042] In yet another embodiment of the invention, the tool head of the surface treatment device is configured to be repeatably attachable and detachable from the robot.

[0043] According to an embodiment of the invention, the surface treatment system comprises one or more sensors configured to record a signal from the tool head indicative of a state of the tool head, a state of the workpiece and / or the interaction between the workpiece and the tool head and to generate sensor data from the recorded signal. The one or more sensors can be arranged on the surface treatment device or another object comprised by the surface treatment system, for example on its robot. In particular, both the surface treatment device and the robot can be equipped with one or more sensors, respectively.

[0044] In yet another embodiment of the invention, the surface treatment system comprises an evaluation unit configured to determine one or more control parameters from the sensor data. In particular, the sensors and the evaluation unit can interact in a feedback loop, wherein the sensors provide the evaluation unit with sensor data and the evaluation unit determines and particularly adjusts the control parameters such as the contact pressure based on the sensor data.

[0045] According to an embodiment of the invention, the robot of the surface treatment system comprises an actuator unit configured to cause at least one of the following: a rotational and / or pivotal movement of the tool head; a translational movement of the tool head; a change of a spatial orientation of the tool head. In particular, the actuator unit can be configured to cause all of the above movements and spatial orientation changes.

[0046] In yet another embodiment of the invention, the robot or its actuator unit is configured such that the movement of the tool head attached to the robot is adjusted such that the tool head can be operated according to the one or more control parameters determined by the evaluation unit. To this end, the robot or its actuator unit is configured to receive the control parameters from the evaluation unit.

[0047] In particular, the evaluation unit, the sensors and the actuator unit are configured to communicate in a feedback loop, wherein the sensors provide the evaluation unit with sensor data and the evaluation unit determines and particularly adjusts the control parameters sent to the robot or its actuator unit. As such, the robot can control the interaction between the tool head and the workpiece during the interaction between the tool head and the workpiece.

[0048] Particularly, the surface treatment system comprises an evaluation unit configured to determine one or more control parameters from the sensor data, wherein the at least one sensor and the evaluation unit are configured to interact in a feedback loop, wherein the at least one sensor provides the evaluation unit with sensor data and the evaluation unit determines and particularly adjusts the control parameters based on the sensor data and / or wherein the evaluation unit is configured to employ a convoluted neural network and / or algorithms such as a K-Nearest-Neighbor model or a support vector machine to predict a state of wear of the tool head and / or the workpiece, as well as geometric or material properties of the workpiece based on the recorded signals.

[0049] A third aspect of the invention relates to a surface treatment method, wherein a tool head with a shape-adaptive portion of the surface treatment device according to the first aspect of the invention or its alternative aspect, or of the surface treatment system according to the second aspect of the invention contacts a surface of a workpiece, wherein said shape-adaptive portion conforms to the surface of the workpiece by plastic or elastic deformation.

[0050] According to an embodiment of the invention, the shape-adaptive portion of the tool head is brought into contact with a surface region of the workpiece with a constant curvature profile, wherein the shape-adaptive portion conforms to a portion of said surface region of the workpiece and wherein the tool head is moved according to a trajectory along said surface region with the constant curvature profile, such that the contact portion of the tool head is moved across a plurality of portions of said surface region with the constant curvature profile. The conforming can in this case be realized both by plastic or elastic deformation. In particular, in the course of the movement according to the trajectory, the contact portion of the tool head is moved across all portions of said surface region with constant curvature profile. For example, the constant curvature profile is formed by a section of the outer surface of a cylinder, wherein the trajectory of the tool head runs along an axis parallel to a cylinder axis.

[0051] In yet another embodiment of the invention, for the contact between the shape-adaptive portion of the tool head and the surface of the workpiece, the tool head adopts a first state in which the shape-adaptive portion of the tool head is flexible for conforming to the surface of the workpiece, whereafter the tool head transitions to a second state in which the shape-adaptive portion of the tool head is stiff and maintains its outer contour, such that the tool head can be used for surface treatment.

[0052] In particular, the shape-adaptive portion of the tool head is adopted to a first state in which the shape-adaptive portion of the tool head is flexible and brought into contact with a surface region of a first workpiece with constant curvature profile, wherein the shape-adaptive portion conforms to a portion of said surface region of the first workpiece, whereafter the tool head is adopted to a second state in which the shape-adaptive portion of the tool head is stiff and maintains its outer contour and wherein the tool head is subsequently moved according to a trajectory along: said surface region of the first workpiece with the constant curvature profile, such that the contact portion of the tool head is moved across a plurality of portions of said surface region with the constant curvature profile, surface regions of the first workpiece with different curvature profiles, so as to adapt the regions with different curvature profiles to the constant curvature profile or a surface of a second workpiece, for adapting a surface profile of the second workpiece to the constant curvature profile of the first workpiece.

[0053] In particular, the trajectory is a continuous trajectory or a trajectory comprising a plurality of separate sections. A continuous trajectory refers to a trajectory of the tool head with respect to the workpiece causing the tool head to remain in contact with the workpiece throughout the entire trajectory, such that large surface areas of the workpiece can be treated particularly using meander-, spiral- or boustrophedon-like trajectories. Alternatively, the tool head can be removed from the workpiece after a first section of the trajectory and moved to another region of the workpiece to continue to treatment in a second section separate from the first section.

[0054] According to an embodiment of the invention, a stiffness of the shape-adaptive portion of the tool head is changed between a first stiffness associated with the first state and a second stiffness associated with the second state.

[0055] According to another embodiment of the invention, signals caused by an interaction between the tool head and the workpiece are recorded by sensors, wherein the signals are indicative of a state of the tool head, a state of the workpiece and / or the interaction between the tool head and the workpiece. In particular, the recorded signals comprise sound signals caused by a mechanical interaction between the tool head and the workpiece. For example, the recorded signals can be used to determine a state of wear of the tool head and / or the workpiece. The recorded signals can also be used to determine a material type of the workpiece.

[0056] In another embodiment of the invention, a contact pressure of the contact between the tool head and the workpiece and / or wherein a stiffness of the shape-adaptive portion is changed based on recorded signals indicative of a state of operation of the tool head, a state of the workpiece and / or an interaction between the tool head and the workpiece, particularly by means of a feedback loop wherein sensors provide an evaluation unit with the sensor data and the evaluation unit determines and particularly adjusts the control parameters sent to a robot or an actuator unit that controls the interaction between the tool head and the workpiece.

[0057] In particular, the feedback loop can be realized by combining pressure data, vibration data, sound data and / or image data recorded by pressure sensors, vibration sensors, microphones and / or cameras into combined data, wherein the evaluation unit determines and particularly adjusts the control parameters sent to a robot or an actuator unit that controls the interaction between the tool head and the workpiece based on the combined data. Such a combination or fusing of different sensor data allows to acquire information based on various different physical parameters such as pressure, vibrations, sounds and optical parameters, allowing to gain comprehensive information regarding the state of operation of the tool head, the workpiece and / or the interaction between the tool head and the workpiece. Moreover, such a combination or fusing can be particularly advantageous if individual sensor data are inaccurate, erroneous or do not allow to draw conclusions about the state of operation of the tool head, the workpiece and / or the interaction between the tool head and the workpiece, which can be compensated or supplemented by other sensor data.

[0058] Particularly, the stiffness of the shape-adaptive portion of the tool head is changed while keeping the shape-adaptive portion in contact with the workpiece. As such, the stiffness of the shape-adaptive portion can be changed dynamically during the interaction between the tool head and the workpiece, particularly based on signals recorded by the sensors monitoring the interaction.

[0059] In an embodiment of the invention, the tool head is moved by a robot such as the robot according to the second aspect of the invention.

[0060] A fourth aspect of the invention relates to a computer program comprising instructions which, when executed on a computer, cause computer to control the surface treatment device according to the first aspect of the invention or its alternative aspect and / or the surface treatment system according to the second aspect of the invention to execute the surface treatment method according to the third aspect of the invention.

[0061] The computer for executing the computer program can be or be comprised by said evaluation unit, which may be part of the surface treatment device according to the first aspect or its alternative aspect of the invention or the surface treatment system according to the second aspect of the invention.

[0062] The evaluation unit can particularly employ a convoluted neural network and / or algorithms such as the K-Nearest-Neighbor model or a support vector machine to predict for example a state of wear of the tool head and / or the workpiece, as well as geometric or material properties of the workpiece based on recorded sensor signals.

[0063] Exemplary embodiments are described below in conjunction with the Figures. The Figures are appended to the claims and are accompanied by text explaining individual features of the shown embodiments and aspects of the present invention. Each individual feature shown in the Figures and / or mentioned in the text of the Figures may be incorporated (also in an isolated fashion) into a claim relating to the first aspect or its alternative aspect, the second aspect, the third aspect and / or the fourth aspect according to the present invention. Figs. 1a-fshow a first embodiment of a surface treatment device according to the invention, wherein the surface treatment device comprises a deformable shell enclosing a volume filled with solid particles for conforming to a surface of a workpiece; Figs. 2a,bshow a second embodiment of a surface treatment device according to the invention with a rigid shell arranged in an upper portion of the tool head; Fig. 3shows a third embodiment of a surface treatment device according to the invention, comprising a microphone for recording sound signals (Fig. 3a) and an active sound sensor with a microphone and a sound emitter (Fig. 3b); Fig. 4shows a fourth embodiment of a surface treatment device according to the invention, comprising a plurality of hinges for performing movements and for changing the orientation of a tool head of the surface treatment device; Fig. 5shows a fifth embodiment of a surface treatment device according to the invention, comprising a plurality of tool heads arranged in a row for conforming to a surface of a workpiece; Fig. 6shows a sixth embodiment of a surface treatment device according to the invention, comprising a plurality of tool heads arranged in two rows for conforming to a surface of a workpiece; Figs. 7a,bshow a seventh embodiment of a surface treatment device according to the invention, comprising cameras for recording images of an edge of a contact portion of the tool head of the surface treatment device; Figs. 8a-cshow an eighth embodiment of a surface treatment device according to the invention, comprising a plurality of pressure sensors for recording pressure signals indicative of a contact pressure between the tool head and a workpiece; Figs. 9a,bshows a ninth embodiment of a surface treatment device according to the invention, comprising a sensor arranged inside a hollow shaft of the surface treatment device; Fig. 10shows an embodiment of a surface treatment system according to the invention, comprising a plurality of vibration sensors for recording vibrations caused by an interaction between the tool head and a workpiece; Figs. 11a-cshow a first embodiment of a computer program according to the invention, wherein recorded sound data are used to determine a state of wear for two workpieces of the same geometry and material; and Figs. 12a-cshows a second embodiment of a computer program according to the invention, wherein recorded sound data are used to determine a state of wear for two workpieces with the same material but different geometry.

[0064] Figs. 1a-f show a first embodiment of a surface treatment device 1 according to the invention.

[0065] Fig. 1a shows the surface treatment device 1 in a perspective view. The surface treatment device 1 comprises a tool head 2 with a shape-adaptive portion 3 for contacting a workpiece 4. Exemplary workpieces 4 are shown in Figs. 1b-f. The tool head 2 according to the present embodiment comprises a deformable shell 5 enclosing a volume filled with solid particles 20 for conforming to a surface of a workpiece 4. The volume enclosed by the deformable shell 5 is in fluid communication with a pressure adjustment unit (not shown) via a tube 9, such that a gas pressure acting on the solid particles 20 inside the deformable shell 5 can be adjusted. By adjusting the gas pressure, a stiffness of the shape-adaptive portion 3 of the tool head 2 can be changed. As such, the tool head 2 is configured to adopt a first state in which the shape-adaptive portion 3 of the tool head 2 and thus a contact portion 5a of the deformable shell 5 is rendered flexible so as to conform to the surface of the workpiece 4 and a second state in which the shape-adaptive portion 3 of the tool head 2 and thus the contact portion 5a of the deformable shell 5 is stiff and maintains its outer contour. The deformable shell 5 comprises an abrasive layer 5b with an abrasive surface for treating surfaces of a workpiece 4. Alternatively, the deformable shell 5 can comprise a polishing- or a capillary layer for treating the surface. In particular, at least sections of the deformable shell 5 that comprise an abrasive-, polishing- or capillary layer are removably attachable and detachable from the shape-adaptive portion 3, such that the surface of the deformable shell 5 can be changed depending on the surface treatment process. Possible surface treatment processes with abrasive- or polishing layers include sanding, grinding and polishing, wherein a capillary layer particularly allows additive surface processing like painting or waxing. The capillary layer can hold an additive substance in a liquid or powder form that can be refilled by dipping the tool head 2 into the liquid or powder.

[0066] As can further be seen in Fig. 1a, the tool head 2 with its shape adaptive portion 3 is connected to a shaft 12 of the surface treatment device 1 that can be used for handling the surface treatment device 1. The surface treatment device 1 can be operated manually by a user holding the surface treatment device 1 by its shaft 12 or optional handles attached to the shaft 12, wherein said pressure adjustment unit can be a manually operable piston pump. Alternatively, the surface treatment device 1 can be operated automatically, for instance by a robot 11 handling the surface treatment device 1 via the shaft 12, similar to the embodiment shown in Fig. 9, in which case the pressure adjustment unit may for example be an electric pump.

[0067] To treat surfaces of a workpiece 4, the surface treatment device 1 can be operated as depicted in Figs. 1b-f and described in the following.

[0068] In Fig. 1b, the surface treatment device 1 approaches a surface of a workpiece having a nonplanar surface to be treated by the surface treatment device 1. To this end, the gas pressure inside the deformable shell 5 acting on the solid particles 20 is kept at a first pressure in which the solid particles 20 are free to move inside the deformable shell 5, such that the tool head adopts said first state. For example, the first pressure corresponds to atmospheric pressure, such that the gas pressure inside the deformable shell 5 essentially corresponds to the gas pressure outside the deformable shell 5.

[0069] Fig. 1c shows the surface treatment device 1 in contact with the surface of the workpiece 4, wherein a contact portion 5a of the deformable shell 5 conforms to the surface of the workpiece 4 as a consequence of the free movement of the solid particles 20, rendering the shape-adaptive portion 3 and the deformable shell 5 flexible. Once the contact portion 5a of the deformable shell 5 has conformed to the surface of the workpiece 4, particularly once a predetermined contact pressure between the tool head 2 and the workpiece 4 has been reached, gas inside the deformable shell 5 is at least partially removed by said pressure adjustment unit so as to decrease the gas pressure acting on the solid particles 20. As a consequence, the shape-adaptive portion 3 of the tool head 2 and its deformable shell 5 undergo a transition to said second state in kind of vacuum stiffening caused by the now restricted freedom of movement of the granulate. For example, the gas pressure inside the deformable shell 5 in the second state can be between 0.5 atm and 0.959 atm. In particular, a stiffness of the shape-adaptive portion 3 of the tool head 2 can be controlled by the second pressure, wherein lower second pressures realize higher stiffnesses and vice versa. This allows to adapt the stiffness according to the intended surface treatment process. For example, the tool head 2 may be moved along the workpiece 4 in order to remove material from the workpiece 4 until the workpiece 4 exhibits a constant curvature profile along at least a section of the workpiece 4, wherein the constant curvature profile corresponds to the curvature profile of the workpiece 4 shown in the cut view of Fig. 1c.

[0070] However, referring to Fig. 1d and Fig. 1e, the surface treatment device 1 according to the present embodiment also allows to adapt a surface profile of one workpiece to another. For example, a surface profile of a second workpiece 4b as the one shown in Fig. 1e, can be adapted to a surface profile of a first workpiece 4a, for instance the one shown in Figs. 1b-d. To this end, the tool head 2 is removed from the first workpiece 4a after conforming to its surface in said first state and a transition to said second state. In the second state, the shape-adaptive portion 3 of the tool head 2 is stiff and maintains its outer contour, even if the tool head 2 and the workpiece 4,4a are no longer in contact, as can be seen in Fig. 1d. Now, as shown in Fig. 1e, the tool head 2 is brought in contact with a second workpiece 4b and moved according to a trajectory along the second workpiece 4,4b for adapting the surface profile of the second workpiece 4b to the surface profile of the first workpiece 4a. This allows to transform for example a cuboid second workpiece 4b into a second workpiece 4b that exhibits at least in portions the surface profile of the first workpiece 4a.

[0071] In another embodiment of a surface treatment method according to the invention, the shape-adaptive portion 3 of the tool head 2 according to the present embodiment is brought into contact with a surface region of a workpiece 4 with a constant curvature profile as shown in Fig. 1f. In this example, the surface region of the workpiece 4 corresponds to the surface of a sphere, such that the curvature of the surface in this surface region is constant. The shape-adaptive portion 3 conforms to a portion of said surface region with constant curvature with the tool head 2 being in said first state. Next, the tool head 2 adopts the second state and becomes stiff, whereafter the tool head 2 is moved according to a trajectory along said surface region with the constant curvature profile, such that the contact portion 5a of the tool head 2 is moved across a plurality of portions of said surface region with the constant curvature profile.

[0072] Even though not shown, the surface treatment device 1 of Figs. 1a-f comprises one or more sensors as disclosed herein, wherein the one or more sensors is configured to record a signal from the tool head 2 indicative of a state of the tool head 2, a state of the workpiece 4 and / or an interaction between the tool head 2 and the workpiece 4 and to generate sensor data from the recorded signal.

[0073] Fig. 2a and Fig. 2b show a second embodiment of a surface treatment device 1 according to the invention.

[0074] The tool head 2 in this embodiment comprises a rigid shell 50 arranged in an upper portion and a shape-adaptive portion 3 with a deformable shell 5 arranged in a lower portion of the tool head 2. This configuration allows only the lower portion of the tool head 2 to conform to the surface of the workpiece 4. The rigid shell 50 limits the deformation and bulging to the lower portion when the tool head 2 interacts with the surface of the workpiece 4. Specifically, the rigid shell 50 spatially stabilizes the shape-adaptive portion 3, ensuring that, during interaction with the workpiece 4, the shape-adaptive portion 3 maintains controlled deformations, preventing irregular movements that could compromise the quality of the surface treatment.

[0075] Fig. 2b shows a cross-sectional view through the shape-adaptive portion 3 of the tool head 2 shown in Fig. 2a. The deformable shell 5 of the shape-adaptive portion 3 at least partially encloses a volume filled with solid particles 20 as in the first embodiment. The deformable shell 5 comprises an elastic layer 5c and an abrasive layer 5b, wherein the elastic layer 5c is arranged between the volume filled with solid particles 20 and the abrasive layer 5b. Hence, when the solid particles 20 jam to render the shape-adaptive portion 3 of the tool head 2 stiff, the elastic layer 5c can deform to fill spaces between individual solid particles 20 at the interface with the deformable shell 5, thereby smoothing and evening out the abrasive layer 5b at the outside of the tool head 2. This enhances the ability of the tool head 2 to conform to the surface of the workpiece 4.

[0076] Even though not shown, the surface treatment device 1 of Fig. 2a and Fig. 2b comprises one or more sensors as disclosed herein, wherein the one or more sensors is configured to record a signal from the tool head 2 indicative of a state of the tool head 2, a state of the workpiece 4 and / or an interaction between the tool head 2 and the workpiece 4 and to generate sensor data from the recorded signal.

[0077] Fig. 3a and Fig. 3b show a third embodiment of the invention. The tool head 2 of the surface treatment device 1 in this embodiment comprises a rigid shell 50 arranged in an upper portion and a shape-adaptive portion 3 with a deformable shell 5 arranged in a lower portion of the tool head 2, as in the second embodiment of Fig. 2a.

[0078] The surface treatment device 1 of Fig. 3a further comprises a sensor 60, particularly a vibration sensor 6 in the sense of a microphone 6a. The microphone 6a is configured to generate sensor data by means of sound data from a recorded sound caused by the interaction between the tool head 2 and the workpiece 4, wherein the sound data comprises the recorded sound signal and / or a spectrum of the recorded sound signal indicative of the interaction between the tool head 2 and the workpiece 4. The recorded sound data are indicative of a state of the tool head 2, a state of the workpiece 4 and / or an interaction between the tool head 2 and the workpiece, such that conclusions regarding the state of the tool head 2, the state of the workpiece 4 and / or the interaction between the tool head 2 and the workpiece can be drawn from the recorded sound signals, particularly from their corresponding sound data. To this end, the recorded sound signals are forwarded to an evaluation unit 8 which includes a computer or processing unit configured to evaluate the recorded sound data. For example, in this context, a machine learning algorithm may be employed. The efficiency of an example machine learning algorithm for this purpose is shown and explained in the context of Figs. 11a-c and Figs. 12a-c.

[0079] Compared to the surface treatment device 1 of Fig. 3a, the surface treatment device 1 of Fig. 3b, additionally comprises a sound emitter 6b configured to emit a sound emitter signal, such that the sound emitter signal can be modulated by an interaction with the tool head 2 and / or by an interaction between the tool head 2 and the workpiece 4, thereby forming the sound signal. The sound emitter 6b emitter emitting the sound emitter signal and the microphone 6a recording the sound signal together form an active sound sensor 60a. The active sound sensor 60a has for example the technical advantage that it allows to probe the morphology of the tool head 2 by exposing it to said sound emitter signal and detecting a modulated sound emitter signal by means of a reflected sound signal reflected from the tool head 2, which is indicative for the morphology of the tool head 2. In other words, the morphology of the tool head 2, that is, its geometrical form and / or internal structure, particularly on the micro- or nanoscale can be understood as the state of the tool head 2. For example, the surface roughness of the contact portion 5a can be considered as the morphology or the state of the tool head 2. To probe the state of the tool head 2, the sound emitter signal can for example be swept within a predetermined frequency spectrum, for example from 20 Hz to 50 kHz, while recording the reflected sound signal. The range of the frequency spectrum depends on the materials of the tool head 2 and the workpiece 4. Such measurements of the sound signals can be repeated after use of the tool head 2 to treat a workpiece 4, wherein changes or trends of the detected sound signals indicate changes of the state of the tool head 2. In the same fashion, the state of the workpiece 4, that is, the morphology, particularly the surface roughness of the workpiece, can be determined by exposing the workpiece 4 to the emission sound signal and recording the reflected sound signal. The state of the tool head 2 and / or the workpiece 4 can be determined by exposing the outer surface of the tool head 2, particularly its contact portion 5a, or an outer surface of the workpiece to be treated to the sound emitter signal, respectively and recording the respective reflected sound signal, when the tool head 2 and the workpiece 4 are not in contact. Conclusions regarding the interaction between the tool head 2 and the workpiece 4 can be drawn from interference between the sound emitter signal and an interaction sound signal caused by the interaction between the tool head 2 and the workpiece 4. The resulting sound signal is a result of modulation of the emission sound signal by means of interference, which sound signal can be detected by the microphone 6a while the tool head 2 and the workpiece 4 are interacting in physical contact with each other.

[0080] While Fig. 3b represents an active sound sensor 60a, the same principle of an active sensor with a signal emitter and a signal detector can be realized by other forms of signals, for example signals based on electromagnetic radiation and / or electricity.

[0081] Fig. 4 shows a fourth embodiment of a surface treatment device 1 according to the invention. This surface treatment device 1 comprises a movement mechanism for performing movements and for changing the orientation of a tool head 2 of the surface treatment device 1. In the present embodiment, the movement mechanism comprises a plurality of hinges 13a,13b,13c,13d. The tool head 2 comprises a shape-adaptive portion 3 configured to conform to a surface of a workpiece 4 by plastic or elastic deformation. For example, the shape-adaptive portion 3 comprises a shape memory material which can plastically deform in order to conform to a surface of a workpiece 4 and maintain the deformation even when the contact between the tool head 2 and the workpiece 4 is released. In another example, the shape-adaptive portion 3 comprises an elastic foam, such that the foam can deform elastically to conform to a surface of a workpiece 4. For example, polyurethane, polypropylene, neoprene, polyethylene can be used as materials to realize the elastic foam. Alternatively, the deformable shell 5 of the shape-adaptive portion 3 can at least partially enclose a closed volume filled with a gas, such that the shape-adaptive portion 3 can deform elastically under a reversible compression of the gas inside the shape-adaptive portion 3 for conforming to the surface of a workpiece 4.

[0082] The movements and orientation changes of the tool head 2 depicted in Fig. 4 can be driven by an actuator mechanism, for example an electrical motor, tendons, pneumatics, or hydraulics. Particularly, in case of tendons, a first tendon can be guided through the shaft 12 of the surface treatment device 1, a first hinge 13a and a second hinge 13b down to a fourth hinge 13d, wherein a second tendon can be guided through the shaft 12 of the surface treatment device 1, the first hinge 13a and a third hinge 13c down to the fourth hinge 13d. By adjusting the length of the respective tendon, the movements and orientation changes can be realized mediated by the hinges 13a,13b,13c,13d and a respective pivoting axis associated with each hinge 13a,13b,13c,13d: For example, if both tendons are pulled or rolled up by an actuator such that they are shortened by the same amount, the tool head 2 will move up along a direction parallel to the vertical arrow indicated in Fig. 4 in a translational movement. However, the tool head 2 may also perform pivoting movements, particularly about the pivoting axis associated with the first hinge 13a, as well as complex changes of orientation of the tool head 2, once the tendons are controlled by the actuator such that their lengths are varied by different amounts.

[0083] In particular, the second hinge 13b and the third hinge 13c can be active hinges that are driven by the actuator mechanism while the first hinge 13a and the fourth hinge 13d are passive hinges that are not driven by the actuator mechanism but contribute a respective degree of freedom defined by their respective pivoting axis.

[0084] Optionally, the surface treatment device 1 can comprise a mantle 16 as indicated in Fig. 4, which circumferentially encloses the hinges 13a,13b,13c,13d. As such, the mantle 16 can protect the hinges 13a,13b,13c,13d and their mechanics for example from particles or dust whirled up from the surface of a workpiece 4 due to the interaction between the tool head 2 and the workpiece 4.

[0085] Even though not shown, the surface treatment device 1 of Fig. 4 comprises one or more sensors as disclosed herein, wherein the one or more sensors is configured to record a signal from the tool head 2 indicative of a state of the tool head 2, a state of the workpiece 4 and / or an interaction between the tool head 2 and the workpiece 4 and to generate sensor data from the recorded signal.

[0086] Fig. 5 shows a fifth embodiment of a surface treatment device 1 according to the invention. The surface treatment device 1 comprises a carrier 15 attached to a shaft 12 for moving or driving the surface treatment device 1, wherein a plurality, in the present example four, tool heads 2 for treating a surface of a workpiece 4 protrude from the carrier 15. In the present embodiment, the tool heads 2 are arranged along a row. Each of the tool heads 2 comprises a respective shape-adaptive portion 3 configured to conform to the surface of the workpiece 4. As such, the surface treatment device 1 can conform to the surface of the workpiece 4 in the sense that each shape-adaptive portion 3 of the plurality of tool heads 2 conforms locally with a respective contact portion 5a of the respective shape-adaptive portion 3 to the surface of the workpiece 4. Moreover, the tool heads 2 can be moved independently of each other, which allows to conform multiple tool heads 2 of the surface treatment device 1 to multiple regions of the surface of the workpiece 4 at the same time. This makes the surface treatment device 1 particularly useful for sub-aperture surface treatment applications, in which the contact portion 5a of an individual tool head is smaller than a surface to be treated.

[0087] The tool heads 2 shown in Fig. 5 each comprise a mantle 16 providing mechanical protection for movement mechanisms arranged inside the mantle 16. For example, as indicated on the left tool head 2 in Fig. 5, each of the tool heads 2 comprises the hinges 13a,13b,13c,13d according to the fourth embodiment of Fig. 4, allowing both for a translational up-and-down-movement as well as pivoting movements and changes of orientation of the tool heads 2 as outlined in more detail in the context of Fig. 4. Hence, the surface treatment device 1 can be driven along an axis along the surface of the workpiece 4 as indicated in Fig. 5 by performing a translational movement of the shaft 12 and the carrier 15, while the individual tool heads 2 conform to the surface of the workpiece 4 and perform said pivoting movements and orientation changes.

[0088] Even though not shown, the surface treatment device 1 of Fig. 5 comprises one or more sensors as disclosed herein, wherein the one or more sensors is configured to record a signal from the tool head 2 indicative of a state of the tool head 2, a state of the workpiece 4 and / or an interaction between the tool head 2 and the workpiece 4 and to generate sensor data from the recorded signal.

[0089] Fig. 6 shows a sixth embodiment of a surface treatment device 1 according to the invention. The surface treatment device 1 comprises a carrier 15 attached to a shaft 12 for moving or driving the surface treatment device 1, wherein a plurality, in the present example six, tool heads 2 for treating a surface of a workpiece 4 protrude from the carrier 15. In the present embodiment, the tool heads 2 are arranged along two parallel rows, wherein each row features three tool heads 2.

[0090] As in the fifth embodiment of Fig. 5, each of the tool heads 2 comprises a mantle 16 providing mechanical protection for movement mechanisms arranged inside the mantle 16. For instance, each of the tool heads 2 can comprise the movement mechanism depicted in the fourth embodiment shown in Fig. 4. Compared to the fifth embodiment of Fig. 5, the present embodiment with two parallel rows provides a larger interaction width between the surface treatment device 1 and the surface of the workpiece 4, if the surface treatment device 1 is moved in a translational movement as shown in Fig. 6. This is because the surface treatment device 1 according to the present embodiment comprises two parallel rows instead of a single row. In contrast, the surface treatment device 1 of the fifth embodiment of Fig. 5 comprises four tool heads 2 arranged in one row, wherein each row in the present embodiment of Fig. 6 only features three tool heads 2. Hence, the surface treatment device 1 of the fifth embodiment of Fig. 5 comprises a larger interaction length between the surface treatment device 1 and the surface of the workpiece 4, if the surface treatment device 1 is moved in a translational movement as shown in Fig. 5 or Fig. 6. The skilled person will appreciate that the number of rows and the number of tool heads 2 per row can be modified depending on the surface of the workpiece and surface treatment process.

[0091] Even though not shown, the surface treatment device 1 of Fig. 6 comprises one or more sensors as disclosed herein, wherein the one or more sensors is configured to record a signal from the tool head 2 indicative of a state of the tool head 2, a state of the workpiece 4 and / or an interaction between the tool head 2 and the workpiece 4 and to generate sensor data from the recorded signal.

[0092] Fig. 7a and Fig. 7b show a seventh embodiment of a surface treatment device 1 according to the invention. As can be seen in the perspective view of Fig. 7a, the present surface treatment device 1 comprises a tool head 2 with a shape-adaptive portion 3 configured to conform to a surface of the workpiece 4 by plastic or elastic deformation. The shape-adaptive portion 3 comprises a deformable shell 5 with a contact portion 5a for contacting the workpiece 4, wherein the contact portion 5a comprises an abrasive layer 5b. Alternatively, the abrasive layer 5b can be a polishing or a capillary layer.

[0093] The present surface treatment device 1 further comprises a base portion 17, wherein the tool head 2 with its shape-adaptive portion 3 is connected to the base portion 17 via a shaft 12. A plurality of cameras 7, for example two or three cameras 7 are arranged on a side of the base portion 17 facing the tool head 2, wherein the cameras 7 are arranged such that they can record images of an edge of the contact portion 5a of the tool head 2, as indicated by dashed lines in Fig. 7b. As such, the cameras are arranged and configured to record the deformation of the shape-adaptive portion 3 during the interaction of the tool head 2 and the surface of the workpiece 4. At the same time, the cameras 7 can be configured to record at least portions of the surface of the workpiece 4, for instance in order to recognize properties of the workpiece 4, for example a roughness or a material of the surface to be treated. The information regarding the interaction between the tool head 2 and the workpiece 4 and / or regarding the properties of the workpiece 4 is encoded in signal data by means of image data generated by the cameras 7, which can be used to adjust a contact pressure of the tool head 2 on the surface of the workpiece 4. For example, if a deformation of the shape-adaptive portion 3 beyond a predetermined limit is detected, the contact pressure can be lowered, wherein if a deformation of the shape-adaptive portion 3 below a predetermined minimum is detected, the contact pressure can be increased. The detection of the deformation can be achieved by means of an evaluation unit 8 (not shown) that evaluates the sensor data my means of image data encoding the recorded images. The evaluation unit 8 can be part of the surface treatment device 1 and / or part of a surface treatment system 10 as disclosed herein, comprising a surface treatment device 1 according to the present embodiment. The evaluation unit 8 can also determine control parameters such as the contact pressure from the sensor data, in the present embodiment from the image data. As such, the cameras 7 and the evaluation unit 8 can interact in a feedback loop, wherein the cameras 7 provide the evaluation unit 8 with sensor data and the evaluation unit 8 determines and particularly adjusts the control parameters such as the contact pressure based on the sensor data.

[0094] Figs. 8a-c show an eighth embodiment of a surface treatment device 1 according to the invention. As can be seen in the perspective view of Fig. 8a, the present surface treatment device 1 comprises a tool head 2 with a shape-adaptive portion 3 configured to conform to a surface of the workpiece 4 by plastic or elastic deformation. The shape-adaptive portion 3 comprises a deformable shell 5 with a contact portion 5a for contacting the workpiece 4, wherein the contact portion 5a comprises an abrasive layer 5b. Alternatively, the abrasive layer 5b can be a polishing or a capillary layer.

[0095] As indicated in dashed lines in Fig. 8a, the present surface treatment device 1 comprises a plurality of pressure sensors 14 extending parallel each other and to a longitudinal axis L of the tool head 2 as well as through at least a section of the shape-adaptive layer 3. Each pressure sensor 14 is configured to record pressure signals indicative of a contact pressure between the tool head 2 and a workpiece 4 at the location of the respective pressure sensor 14.

[0096] As can be best seen in Fig. 8b, where the abrasive layer 5b has been removed for better visibility, the pressure sensors 14 are arranged in regular pattern. In the present embodiment, the regular pattern is defined by two concentric circles around the longitudinal axis L of the tool head 2. The pressure sensors 14 are positioned equidistantly from each other within each circle, and both circles are concentric with the longitudinal axis L. As a consequence of the regular pattern, the pressure sensors 14 according to the present embodiment record pressure signals that allow to derive an effective contact surface between the tool head 2 and the surface of the workpiece 4 as well as a spatial pressure distribution that quantifies the pressure load in different areas of the tool head 2. The skilled person will appreciate that the number and distribution of the pressure sensors 14 can vary depending on the workpiece 4 and / or surface treatment process.

[0097] Fig. 8c shows a side view of the tool head 2 according to the present embodiment, wherein individual pressure sensors 14 are indicated as dashed lines.

[0098] The pressure sensors 14 can comprise for example piezoelectric, optical, resistive, capacitive, microelectromechanical systems, force-sensitive resistors, or Hall Effect pressure sensors. The detection and quantification of the pressure can be achieved by means of an evaluation unit 8 (not shown) evaluating sensor data my means of the pressure data encoding the recorded pressures, wherein the pressure data are generated by the pressure sensors 14. The evaluation unit 8 can be part of the surface treatment device 1 and / or part of a surface treatment system 10 as disclosed herein, comprising a surface treatment device 1 according to the present embodiment. The evaluation unit 8 can also determine control parameters such as the contact pressure from the sensor data, in the present embodiment from the pressure data. As such, the pressure sensors 14 and the evaluation unit 8 can interact in a feedback loop, wherein the pressure sensors 14 provide the evaluation unit 8 with sensor data and the evaluation unit 8 determines and particularly adjusts the control parameters such as the contact pressure based on the sensor data.

[0099] Fig. 9a and Fig. 9b show a ninth embodiment of a surface treatment device 1 according to the invention. As can be seen in the perspective view of Fig. 9a, the present surface treatment device 1 comprises a tool head 2 with a shape-adaptive portion 3 configured to conform to a surface of the workpiece 4 by plastic or elastic deformation. The shape-adaptive portion 3 comprises a deformable shell 5 with a contact portion 5a for contacting the workpiece 4, wherein the contact portion 5a comprises an abrasive layer 5b. Alternatively, the abrasive layer 5b can be a polishing or a capillary layer. As indicated already in dashed lines in Fig. 9a and best seen in the cross-sectional view through the surface treatment device 1 shown in Fig. 9b, the surface treatment device 1 comprises a sensor 60 arranged in an opening 18 of the shape-adaptive portion 3 and its abrasive layer 5b, wherein the sensor 60 is configured to record signals caused by an interaction between the tool head 2 and the surface of a workpiece 4 and to generated corresponding sensor data. As such, the sensor 60 is located in close proximity to the abrasive layer 5b, and, in operation, to the surface of the workpiece 4, such that the recorded signals are particularly indicative of a state of the tool head 2, a state of the workpiece 4 and / or an interaction between the tool head 2 and the workpiece 4. To this end, the sensor 60 may for example be placed at a distance of 0.5 mm to 50 mm with respect to the abrasive layer 5b, which is typically close enough to record valuable signals during the interaction between the tool head 2 and the workpiece 4. In particular, this arrangement allows the sensing of local surface properties of the workpiece 4 and / or material or abrasive removal without affecting the abrasive process. For example, the sensor 60 comprises at least one or all of the following: a vibration sensor 6; a microphone 6a; a camera 7; an accelerometer.

[0100] The tool head 2 may for example be realized in spherical shapes, such as the ones shown in the embodiments of Figs. 1a-f to 3; tubular structures, such as the ones shown in the embodiments of Fig. 5 and 6 or other geometric shapes. Exemplary dimensions of the tool head can range from the millimeter range into the meter range and higher, depending on the dimensions of the workpiece to be treated with the tool head 2.

[0101] The sensor 60 can communicate with an evaluation unit 8 (not shown) of the surface treatment device 1 and / or a surface treatment system 10 as disclosed herein, for example by means of wires 61 that are guided through a hollow shaft 12 of the surface treatment device 1. Alternatively, the sensor 60 can communicate with the evaluation unit 8 by means of wireless communication techniques. The evaluation unit 8 can also determine control parameters such as the contact pressure from the sensor data. As such, the sensor 60 and the evaluation unit 8 can interact in a feedback loop, wherein the sensor 60 provides the evaluation unit 8 with sensor data and the evaluation unit 8 determines and particularly adjusts the control parameters such as the contact pressure based on the sensor data.

[0102] Fig. 10 shows an embodiment of a surface treatment system 10 according to the invention. The surface treatment system 10 comprises a surface treatment device 1 which comprises a tool head 2 with a shape-adaptive portion 3 configured to conform to a surface of the workpiece 4 by plastic or elastic deformation. The shape-adaptive portion 3 comprises a deformable shell 5 with a contact portion 5a for contacting the workpiece 4, wherein the contact portion 5a comprises an abrasive layer 5b. Alternatively, the abrasive layer 5b can be a polishing or a capillary layer.

[0103] The surface treatment device 1 is connected to a robot 11 of the surface treatment system 10 via a shaft 12 of the surface treatment device 1, such that the tool head 2 can be moved by the robot 11. As can further be seen in Fig. 10, the present surface treatment system 10 comprises a plurality of vibration sensors 6, particularly microphones 6a, which are configured to record vibration signals, particularly sound signals and to generate corresponding vibration data, particularly sound data. These signals can be caused by an interaction between the tool head 2 and the surface of the workpiece 4. The vibration sensors 6, particularly the microphones 6a, are arranged at various positions: on the tool head 2, on the shaft 12, on the robot 11, particularly on a side of the robot facing the tool head 2 and, in operation, the surface of the workpiece 4. As such, the signals recorded by the vibration sensors 6, particularly the microphones 6a comprise detailed information that allow to draw conclusions of a state of the tool head 2, a state of the workpiece 4 and / or an interaction between the tool head 2 and the workpiece 4.

[0104] Fig. 10 also shows an evaluation unit 8 configured for wireless communication with the vibration sensors 6, particularly the microphones 6. The evaluation unit 8 can determine control parameters such as the contact pressure from the sensor data received from the individual vibration sensors 6, particularly the microphones 6. As such, the vibration sensors 6, particularly the microphones 6, and the evaluation unit 8 can interact in a feedback loop, wherein the vibration sensors 6, particularly the microphones 6 provide the evaluation unit 8 with sensor data and the evaluation unit 8 determines and particularly adjusts the control parameters such as the contact pressure based on the sensor data. To this end, the evaluation unit 8 is configured to communicate with an actuator unit (not shown) of the surface treatment system 10, such that the robot 11 and thus the tool head 2 can be driven based on the control parameters determined by the evaluation unit 8.

[0105] Optionally, the surface treatment devices 1 according to the embodiments shown in Figs. 1a-f, Figs. 2a,b, Figs. 3a,b, Fig. 4, Fig. 5, Fig. 6, Figs. 7a,b, Figs. 8a-c and Figs. 9a,b can each comprise a robot 11 and particularly an evaluation unit 8 according to the present embodiment of Fig, 9, such that the respective surface treatment device 1 can be moved by the robot 11.

[0106] Figs. 11 a-d show a first embodiment of a computer program according to the invention, wherein recorded sound data are used to determine a state of wear of a tool head 2 comprising a shape-adaptive portion 3 with a deformable shell 5 comprising an abrasive layer 5b, as for example in the embodiment of Fig. 2a and Fig. 2b. The recorded sound data are generated by at least one microphone 6a, for example one of the microphones 6a of the embodiment shown in Fig. 10, based on recorded sound signals caused by a mechanical interaction between the tool head 2 and the workpiece 4. The purpose of the computer program according to the present example is to determine a state of wear of the abrasive layer 5b caused by of sanding a workpiece 4. In the present embodiment, the abrasive layer 5b was realized as sandpaper with a certain grit by means. A flat piece of wood was used as the workpiece 4. The state of wear shall be determined in terms of a binary classification of "new sandpaper" and "old sandpaper", wherein the old sandpaper comprises a state of wear with a higher degree of wear than the new sandpaper.

[0107] To this end, the microphone 6a records sound signals and generates corresponding sound data of consecutive sound segments in the time-domain. Fig. 11a shows an example for one sound segment with an exemplary length of 1 second. Next, the sound data of the individual sound segments are evaluated by the evaluation unit 8, which generates a frequency spectrum of the individual sound segments, as shown in Fig. 11b. In the present embodiment, frequency spectra were determined for i) unused sandpaper (new sandpaper) in contact, ii) used sandpaper (old sandpaper) in contact, iii) and the with tool head 2 not being in contact with a given workpiece 4 for a given sandpaper kernel size. For each condition designated i), ii) and iii) above, 2048 frequency spectra have been determined.

[0108] Such frequency spectra are fed into a learning algorithm and used to evaluate the learned model. To accelerate the learning, the algorithm can make use of inputs about characteristic regions in the spectrum, such as known echo effects or wave refractions to identify relevant patterns more quickly. In the present embodiment, the algorithm learns to differentiate between the two discrete states of wear of new and old sandpaper. However, it can also be trained to predict continuous changes, i.e. to quantify a degree of wear beyond a binary classification. The learning can for example be realized based on a K-Nearest-Neighbor model or a support vector machine. These models can be trained quickly and efficiently, for example, to recognize the condition of the sandpaper or the workpiece 4.

[0109] Fig. 11c shows the output of the present computer program. With a prediction quality of 100%, the computer program has identified the two states of wear of the abrasive layer 5b, new sandpaper and old sandpaper, as well as the third condition in which the tool head 2 was not in contact with the workpiece 4.

[0110] Figs. 12a-c show a second embodiment of a computer program according to the invention, wherein recorded sound data are used to determine a state of wear of abrasive layer 5b. In the present embodiment, the investigated workpieces 4 comprised the same material and sandpaper with given kernel, as in the embodiment of Figs. 11a-c. However, other than in the embodiment of Figs. 11a-c, the workpieces 4 in the present embodiment did not have the same geometry but different geometries, which introduces an additional variable and thus makes the determination of the state of wear more complex.

[0111] To account for the increased complexity, the computer program of the present embodiment uses a convoluted neural network (CNN) instead of more basic machine learning models such as support vector machine. Fig. 12a depicts input data for the CNN. The sound data generated by the microphones 6a are converted by the evaluation unit 8 to two-dimensional, image-like representations as shown in Fig. 12a. The images depict different parametric representation of the recorded sound data, particularly frequency, amplitude, spectrum, Linear-Frequency Cepstral Coefficients, Croma, Cetroid and Bandwidth. The three images visually represent the relevant features of the sounds, which the CNN can process. Besides the sound data, additional inputs, for example contact pressure data between the tool head 2 and the workpiece 4 can be added as an input to the CNN. For example, if there's a pressure distribution map of the tool head, it could be added as an additional input to provide more context. This additional information helps the CNN to make more accurate predictions by considering both the sound features and mechanical factors such as the applied contact force during the interaction between the tool head 2 and the workpiece 4.

[0112] The CNN is schematically depicted in Fig. 12b. In convolutional layers of the CNN important features within the input images are automatically detected, particularly specific frequency patterns indicating worn abrasive layer 5b, particularly sandpaper, echoes or resonances that hint at the type of material or variations in amplitude that could indicate different interactions between the tool head 2 and the workpiece 4. After the convolutional layers, the CNN applies pooling layers, which reduce the dimensionality of the data while retaining essential information. After the feature extraction of the input realized by convolution and pooling, the CNN passes the processed data through fully connected layers. Here, the extracted features are flattened and fed into a fully connected network of minimum two layers. These layers perform the actual classification or regression, predicting outcomes like. In the present embodiment, these layers perform the prediction regarding the state of wear of abrasive layer 5b generalized for workpieces of the same material but different geometries.

[0113] The output predictions are shown in Fig. 12c. The present computer program identified new sandpaper with an accuracy of 83% and old sandpaper with an accuracy of 74%. Compared to support vector machine-based methods, the CNN leads to a significant increase of the prediction accuracy by 29%, when workpiece geometry changes.

[0114] Alternative to the binary prediction of old and new sandpaper, the prediction can also comprise a wear value on a continuous scale, wherein for example 0 corresponds to no wear and 100 to strong wear.

[0115] In the present embodiment, the analyzed workpieces 4 differed in terms of their geometry, while comprising the same material. However, computer programs according to the invention can likewise be used to for example identify a type of material of a workpiece 4 and / or a geometry of the workpiece. In the same fashion, the computer programs according to the invention can be used to determine a state of the tool head 2 and / or the interaction between the tool head 2 and the workpiece 4.

[0116] Optionally, the output of the computer program - for example the prediction for the wear of the abrasive layer 5b or the state of the tool head 2 - can be used to derive and output a recommended action to a user. For example, if strong wear of the abrasive layer 5b is detected, a surface treatment system 10 according to the invention, for example the one of Fig. 10, may output a signal to a user that prompts the user to exchange the abrasive layer 5b and / or the workpiece 4 or to adjust the contact pressure between the tool head 2 and the workpiece 4. Alternatively, the prediction for the wear of the abrasive layer 5b or the state of the workpiece 4 - can be used to generate control data by means of the evaluation unit 8 that cause the robot 11 controlled by the evaluation unit 8 for instance to adjust the interaction between the tool head 2 and the workpiece 4, for instance by means of an adjustment of the contact pressure. List of reference signsSurface treatment device1Tool head2Shape-adaptive portion3Workpiece4First workpiece4aSecond workpiece4bDeformable shell5Contact portion5aAbrasive layer5bElastic layer5cVibration sensor6Microphone6aSound emitter6bCamera7Evaluation unit8Tube9Surface treatment system10Robot11Shaft12Hinge13First hinge13aSecond hinge13bThird hinge13cFourth hinge13dPressure sensor14Carrier15Mantle16Base portion17Opening18Solid particles20Rigid shell50Sensor60Active sound sensor60aWire61Longitudinal axisL

Claims

1. A surface treatment device (1) comprising a tool head (2) with a shape-adaptive portion (3) for contacting a workpiece (4), wherein said shape-adaptive portion (3) is configured to conform to a surface of the workpiece (4) by plastic or elastic deformation, wherein the surface treatment device (1) comprises one or more sensors (6,14,60) configured to record a signal from the tool head (2) indicative of a state of the tool head (2), a state of the workpiece (4) and / or an interaction between the tool head (2) and the workpiece (4) and to generate sensor data from the recorded signal.

2. The surface treatment device (1) according to claim 1, wherein the one or more sensors (6,14,60) comprises at least one an active sensor, the active sensor comprising: - an emitter unit configured to emit an emitter signal, such that the emitter signal can be modulated by an interaction with the tool head (2), the workpiece (4) and / or by an interaction between the tool head (2) and the workpiece (4), thereby forming said signal, and - a detector unit configured to record the signal.

3. The surface treatment device (1) according to claim 2, wherein the emitter unit is arranged and configured to emit the emitter signal into an internal space of the tool head (2), wherein the internal space is delimited from the workpiece (4) by the shape-adaptive portion (3), when the shape-adaptive portion (3) conforms to the surface of the workpiece (4), such that the signal can be formed in the internal space of the tool head (2), and wherein the detector unit is arranged and configured to record the signal formed in the internal space of the tool head (2).

4. The surface treatment device (1) according to one of the preceding claims, wherein the tool head (2) comprises a deformable shell (5) arranged on or forming an outer surface of the shape-adaptive portion (3), wherein the tool head (2) is configured to adopt a first state in which the shape-adaptive portion (3) of the tool head (2) and thus a contact portion (5a) of the deformable shell (5) is rendered flexible so as to conform to the surface of the workpiece (4), and a second state in which the shape-adaptive portion (3) of the tool head (2) and thus the contact portion (5a) of the deformable shell (5) is stiff and maintains its outer contour, wherein the deformable shell (5) encloses a volume filled with solid particles (20).

5. The surface treatment device (1) according to claim 4, wherein the tool head (2) is configured to switch to the first and the second state or to transition to and between the first and the second state by adjusting a gas pressure acting on an inside of the deformable shell (5).

6. The surface treatment device (1) according to one of the preceding claims, wherein the one or more sensors (6,14,60) comprise a vibration sensor (6) configured to record a vibration signal from the tool head (2) indicative of a state of the tool head (2), a state of the workpiece (4) and / or an interaction between the tool head (2) and the workpiece (4) and to generate sensor data by means of vibration data from the recorded vibration signal.

7. The surface treatment device (1) according to claim 6, wherein the vibration sensor (6) is an active vibration sensor, the active vibration sensor comprising: - a vibration emitter unit configured to emit a vibration emitter signal, such that the vibration emitter signal can be modulated by an interaction with the tool head (2), the workpiece (4) and / or by an interaction between the tool head (2) and the workpiece (4), thereby forming the vibration signal, and - a vibration detector unit configured to record the vibration signal.

8. The surface treatment device (1) according to claim 6 or 7, wherein the vibration sensor (6) comprises a microphone (6a) configured to generate sensor data by means of sound data from a recorded sound caused by the interaction between the tool head (2) and the workpiece (4), wherein the sound data comprises the recorded sound signal and / or a spectrum of the recorded sound signal indicative of the interaction between the tool head (2) and the workpiece (4).

9. The surface treatment device according to claim 8, wherein the vibration sensor (6) is an active sound sensor (60a), comprising: - a sound emitter (6b) configured to emit a sound emitter signal, such that the sound emitter signal can be modulated by an interaction with the tool head (2), the workpiece (4) and / or by an interaction between the tool head (2) and the workpiece (4), thereby forming the sound signal, and - said microphone (6a).

10. The surface treatment device (1) according to one of the claims 2 to 9, comprising an active optical sensor, the active optical sensor comprising: - an optical emitter configured to emit electromagnetic radiation, such that the electromagnetic radiation can be modulated by an interaction with the tool head (2), the workpiece and / or by an interaction between the tool head (2) and the workpiece (4), thereby forming an optical signal, and - an optical detector configured to record the optical signal.

11. The surface treatment device (1) according to claim 10, wherein the optical emitter is arranged and configured to emit electromagnetic radiation into the internal space of the tool head (2), such that the optical signal can be formed in the internal space of the tool head (2), and wherein the optical detector is arranged and configured to record the optical signal formed in the internal space of the tool head (2).

12. The surface treatment device (1) according to one of the claims 2 to 11, comprising an active electrical sensor, the active electrical sensor comprising: - an electrical emitter unit configured to emit an electrical emitter signal, such that the electrical emitter signal can be modulated by an interaction with the tool head (2), the workpiece (4) and / or by an interaction between the tool head (2) and the workpiece (4), thereby forming an electrical signal, and - an electrical detector unit configured to record the electrical signal.

13. A surface treatment system (10), comprising a surface treatment device (1) according to one of the claims 1 to 12, as well as a robot (11), wherein the surface treatment device (1) is attached or configured to be attached to the robot (11), such that the surface treatment device (1) can be moved by the robot (11).

14. The surface treatment system (10) according to claim 13, comprising an evaluation unit (8) configured to determine one or more control parameters from the sensor data, wherein the at least one sensor (6) and the evaluation unit (8) are configured to interact in a feedback loop, wherein the at least one sensor (6) provides the evaluation unit (8) with sensor data and the evaluation unit (8) determines and particularly adjusts the control parameters based on the sensor data and / or wherein the evaluation unit (8) is configured to employ a convoluted neural network and / or algorithms such as a K-Nearest-Neighbor model or a support vector machine to predict a state of wear of the tool head (2) and / or the workpiece (4), as well as geometric or material properties of the workpiece (4) based on the recorded signals.

15. A surface treatment method, wherein a tool head (2) with a shape-adaptive portion (3) of the surface treatment device (1) according to one of the claims 1 to 12 or of the surface treatment system (10) according to claim 13 or 14 contacts a surface of a workpiece (4), wherein said shape-adaptive portion (3) conforms to the surface of the workpiece (4) by plastic or elastic deformation.

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