Patent Publication Number: US-2020282293-A1

Title: Footpad with sensor compatibility

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Application No. 62/815,285, entitled “FOOTPAD WITH SENSOR COMPATIBILITY”, and filed on Mar. 7, 2019. The entire contents of the above-listed application are hereby incorporated by reference for all purposes. 
    
    
     FIELD 
     The present description relates generally to a footpad for a personal transport device. 
     BACKGROUND AND SUMMARY 
     Mobile boards used as personal transport devices have evolved dramatically. A variety of options for board shapes, materials, dimensions, and accessories have broadened the range of personal transport device applications and customizability. In recent years, motorized skateboards, in particular, have become a desirable method of personal transportation. As an example, some motorized skateboards resemble traditional skateboards with wheels positioned below a deck of the skateboard, at least one wheel proximate to an end of the skateboard. The motorized skateboards may be adapted with a motor delivering power to the wheels as well as weight sensor controls and/or a handheld throttle for controlling speed. 
     Another example of a motorized skateboard may have, instead of wheels at each end of the skateboard, a single wheel positioned at a central region of the skateboard deck and protruding through the deck. The wheel may be similarly powered by an electric motor and a pressure sensor may be arranged in a front end of the skateboard deck. Thus movement of the motorized skateboard may be controlled by adjusting weight placed on a lead foot of an operator. 
     For enhanced control of a skateboard, it may be desirable to provide concavity in an upper surface of the deck. For example, by configuring a peripheral border of the deck to be thicker than a central region of the deck, the operator may experience greater responsiveness from the skateboard to minute adjustments in weight transfer communicated through the operator&#39;s feet. A geometry of the deck of the motorized skateboard, however, may not be readily adapted to include a concave curvature due to the incorporation of sensors within the deck. Alternatively, optional concave footpads may be added to an upper surface of the deck. However, the footpads may not transmit shifts in weight distribution from the operator&#39;s feet, rendering the weight/pressure sensor unresponsive and inhibiting speed and directional control of the motorized skateboard. 
     The inventors herein have recognized the issue described above and have provided an approach for enabling implementation of concavity in a surface of a personal transport device while maintaining effectiveness of a pressure sensor in the device. The issue may be addressed by a footpad including a concave upper face and a planar lower face, the lower face opposite of the upper face and configured to be coupled to a pressure sensing device, and a central region of the footpad forming a planar section of the lower face configured to be positioned directly above the pressure sensing device. In this way, an operator may obtain greater responsiveness from the personal transport device during maneuvering of the device without sacrificing sensor sensitivity that may otherwise degrade speed control. 
     As one example, a footpad may be molded from a flexible material with a concave shape. The footpad material may balance enough rigidity to resist permanent deformation from the operator&#39;s weight with sufficient pliability to transmit shifts in weight distribution within at least one of the operator&#39;s feet. The footpad may be manufactured in a low-cost manner that allows a geometry of the footpad to be readily customized. Thus the footpad may be retrofitted to a wide variety of personal transport devices while allowing the operator&#39;s riding experience to be optimizable. 
     It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example of a motorized personal transport device adapted with at least one pressure sensor for controlling a speed of the personal transport device. 
         FIG. 2  shows an example of the motorized personal transport device with an operator positioned on the device. 
         FIG. 3A  shows an example of a sensor assembly that may be incorporated in the personal transport device. 
         FIG. 3B  shows an exploded view of the sensor assembly of  FIG. 3A . 
         FIG. 4  shows an example of a set of footpads from a first perspective view that may be applied to a surface of the personal transport device of  FIG. 1 . 
         FIG. 5  shows the set of footpads from a birds-eye view. 
         FIG. 6  shows the set of footpads from a profile view. 
         FIG. 7  shows the set of footpads from a front view. 
         FIG. 8  shows the set of footpads from a second perspective view. 
         FIG. 9  shows a first cross-section of a footpad of the set of footpads. 
         FIG. 10  shows a second cross-section of a footpad of the set of footpads. 
         FIG. 11  shows a positioning of a set of footpads on a personal transport device. 
         FIG. 12  shows an example of an adhesive that may be used to couple a set of footpads to a personal transport device. 
         FIG. 13  shows an example of a textured layer that may be adhered to an upper surface of a set of footpads. 
         FIG. 14  shows a schematic diagram of a first footpad of a set of footpads with a first amount of curvature. 
         FIG. 15  shows a schematic diagram of a second footpad of a set of footpads with a second amount of curvature. 
         FIG. 16  shows an exploded view of a wheel assembly that may be included a personal transport device. 
         FIG. 17  shows an example of a method for manufacturing a set of footpads for a personal transport device. 
         FIG. 18A  shows an exploded view of a platform of a deck of a PT device configured with a rider detection device and a concave footpad. 
         FIG. 18B  shows a cross-section of the platform of  FIG. 18A . 
         FIG. 19A  shows a first alternative embodiment of a footpad from a birds-eye view. 
         FIG. 19B  shows the first alternative embodiment of the footpad from a profile view. 
         FIG. 20A  shows a second alternative embodiment of a footpad from a birds-eye view. 
         FIG. 20B  shows the second alternative embodiment of the footpad from a profile view. 
         FIG. 21A  shows a third alternative embodiment of a footpad from a birds-eye view. 
         FIG. 21B  shows the third alternative embodiment of the footpad from a profile view. 
         FIG. 22A  shows a fourth alternative embodiment of a footpad from a birds-eye view. 
         FIG. 22B  shows the fourth alternative embodiment of the footpad from a profile view. 
         FIG. 23A  shows a fifth alternative embodiment of a footpad from a birds-eye view. 
         FIG. 23B  shows the fifth alternative embodiment of the footpad from a profile view. 
         FIG. 24A  shows a sixth alternative embodiment of a footpad from a birds-eye view. 
         FIG. 24B  shows the sixth alternative embodiment of the footpad from a profile view. 
         FIGS. 1-13, 16, and 18A-24B  are shown approximately to scale. 
     
    
    
     DETAILED DESCRIPTION 
     The following description relates to systems and methods for a personal transport device. The personal transport device may be a motorized skateboard, as shown in  FIG. 1 . The motorized skateboard may have a deck and a wheel disposed in a central region of the deck. An operator may stand on the deck so that the operator&#39;s feet are positioned on either side of the wheel, as shown in  FIG. 2 . At least one side of the deck may include a sensor, arranged immediately below one of the operator&#39;s feet. An example of a sensor adapted to respond to changes in pressure is shown in  FIG. 3A  and in an exploded view in  FIG. 3B . In order to maintain an efficiency of the sensor in responding to change in pressure, a set of concave footpads may be added to the deck of the motorized skateboard to both allow the sensor to remain effective towards speed control of the motorized skateboard and to increase a responsiveness of the motorized skateboard to changes in direction as indicated by the operator. Various views of the set of footpads is shown in  FIGS. 4-8 , cross-sectional views of the set of footpads are depicted in  FIG. 9-10 , and schematic diagrams of a first footpad with a first degree of curvature and a second footpad with a second degree of curvature are shown in  FIGS. 14-15 . One footpad of the set of footpads is shown coupled to a deck of a motorized skateboard in  FIG. 11 , sandwiched between the deck and a textured layer that provides traction for the operator&#39;s feet. The set of footpads may be secured to the deck by an adhesive, an example of which is shown in  FIG. 12 . An example of the textured layer that may be coupled to a top surface of the set of footpads is shown in  FIG. 13 . An exploded view of a wheel assembly, including a motor powering the motorized skateboard and an axle is illustrated in  FIG. 16 . The set of footpads may be formed from a flexible material and molded via an exemplary manufacturing method described in  FIG. 17 . An exploded view of a platform is shown in  FIG. 18A  and a cross-section of the platform is shown in  FIG. 18B , the platform including a pressure transducer of a rider detection device with a footpad, such as a footpad of the set of footpads described with reference to  FIGS. 4-11, 14-15, and 17 , coupled to the platform. The platform may be included in a deck of a PT device. Alternative embodiments of a footpad are shown in  FIGS. 19A-24B . 
       FIGS. 1-16, and 18A-24B  show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example. 
     Turning now to  FIGS. 1 and 2 , an example of a personal transport (PT) device  100  is shown. The PT device  100  may be a self-stabilizing motorized skateboard including a deck  102  and a wheel assembly  104 . A set of reference axes  106  are provided for comparison between views, indicating a y-axis, an x-axis, and a z-axis. In some example, the y-axis may be parallel with a vertical direction, the x-axis parallel with a horizontal axis, and the z-axis perpendicular to both the y-axis and the x-axis. 
     The deck  102  may be a structure for supporting an operator&#39;s feet, as shown in  FIG. 2 , and includes a frame  108 , a first platform  110 , and a second platform  112 . The deck  102  may be formed from a hard, durable material, such as wood or metal or carbon fiber, etc. The deck  102  may have a rectangular outer geometry when viewed along the y-axis, with a length  114  of the PT device  100 , defined along the z-axis, longer than a width  116 , defined along the x-axis, and the width  116  greater than a thickness  118  of the PT device, the thickness  118  measured along the y-axis, depicted in  FIG. 1 . The first platform  110  and the second platform  112  may be of the same physical piece, or may be separate pieces and both platforms may be mounted to the frame  108 . As shown in  FIG. 2 , the first platform  110  may be configured to support a first foot  103  of the operator and the second platform  112  may be configured to support a second foot  105  of the operator. 
     A direction of forward motion of the PT device  100  is indicated by arrow  120 . As such, the first foot supported by the first platform  110  may be a lead foot of the operator and the first platform  110  is positioned at a front end  122  of the PT device  100 . The second foot supported by the second platform  112  may be a rear foot of the operator and the second platform is positioned a rear end  124  of the PT device  100 . The first platform  110  may be covered with a first textured layer  126  and the second platform  112  may be covered with a second textured layer  128  to provide traction between the operator&#39;s feet and upper surfaces of the platforms. The first and second textured layers  126  and  128  may be a non-slip material such as “grip tape”, coupled directly to the upper surfaces of the first platform  110  and the second platform  112 . 
     The wheel assembly  104  is arranged between the first platform  110  and the second platform  112  and protrudes above the deck  102  and below the deck  102 , with respect to the y-axis through an opening  107  in the deck  102 . The wheel assembly  104  includes a component that is in contact with a ground surface. The component may be a wheel  130 , or a tire or a continuous track. The wheel  130  may be mounted to a motor assembly  136  which may mounted to the frame  108 . The wheel assembly  104 , including the motor assembly  136 , is shown in exploded view  1600  in  FIG. 16 . Components in  FIG. 16  that are similar to components of  FIGS. 1 and 2  are similarly numbered. The wheel assembly  104  may include an axle  1601  extending through a central region of the wheel  130 , along the x-axis and coupled to the frame  108  of the deck  102  of  FIGS. 1 and 2  by axle mounts  1602  and fasteners  1604  in  FIG. 16 . 
     The motor assembly  136  includes a hub motor  1606  which may be positioned in an opening  1608  of the wheel  130 . The axle  1601  may be inserted through a central aperture  1610  of the hub motor  1606  and the axle  1601 , hub motor  1606  may be secured in place by mounting flanges  1612 , hub adapters  1614 , a plurality of bolts  1616 , and various other fastening components. In one example, the hub motor  1606  may be a direct-drive transverse flux brushless motor providing torque output to power motion of the PT device  100  of  FIGS. 1 and 2 . In other examples, the hub motor  1606  may be any apparatus and/or motor suitable for driving rotation of the wheel  130  around the axle  1601 . The hub motor  1606 , wheel  130  and other coupling components of the wheel assembly  104  may be connected together as a subassembly and integrated and installed into the PT device  100 . For example, a plurality of bolts, connecting mounts, and electrical connections (not shown) may be used to couple the wheel assembly  104  to the deck  102  of the PT device  100 . 
     Returning to  FIG. 2 , the frame  108  of the deck  102  of the PT device  100  has a first longitudinal side  132 , extending from the front end  122  to the rear end  124  of the PT device  100  along the z-axis as well as a second longitudinal side parallel with the first longitudinal side and on an opposite side of the PT device  100  (not shown in  FIG. 2 ). The first longitudinal side  132  may include a side-skid pad  134  to provide a barrier between an outer surface of the first longitudinal side  132  and the ground surface if the PT device  100  is, for example, flipped on its side. The second longitudinal side may be similarly disposed with a side-skid pad. It will be appreciated that the side-skid pad  134  may vary in extension along a length of the first longitudinal side, e.g., along the z-axis, without departing from the scope of the present disclosure. 
     The PT device  100  may also include a first partial fender  138 , coupled to the frame  108  and the first platform  110  and a second partial fender  140 , coupled to the frame and the second platform  112 . Each of the partial fenders may extend across the width, e.g., the width  116  of  FIG. 1 , of the deck  102 . The first and second partial fenders  138 ,  140  may inhibit transfer of debris from the wheel  130  to the deck  102  when the wheel  130  is rotating. In other examples, the PT device  100  may have a full fender, entirely covering a portion of the wheel  130  protruding above the deck  102 . The first and second partial fenders  138 ,  140  may be formed from a flexible or resilient material, such as plastic. 
     The PT device  100  is shown in  FIG. 2  with a pitch axis A 1 , parallel with the x-axis, a roll axis A 2 , parallel with the z-axis, and a yaw axis A 3 , parallel with the y-axis. The pitch axis A 1  may be an axis about which the wheel  130  is rotated by the motor assembly  136 , passing through the axle (e.g., the axle  1601  of  FIG. 16 ), the rotation driving motion of the PT device  100  along the z-axis. Tilting of the deck  102  relative to the pitch axis A 1 , as adjusted by the operator, enables speed control of the PT device. For example, when the deck  102  is parallel with the x-z plane, e.g., when the operator stands on the first and second platforms  110 ,  112  with equal weight distribution between the first foot  103  and the second foot  105  and between a forefoot and a heel of the first foot  103 , the motor assembly  136  of the PT device  100  may be activated. Increasing weight on the first foot  103 , which may tilt the front end  122  of the PT device  100  downwards, with respect to the y-axis, indicates forward movement of the PT device  100  is desired. When in motion, decreasing weight on the first foot  103  may decrease the forward speed of the PT device  100 . Tilting the rear end  124  downwards, with respect to the y-axis may also result in halting of the PT device  100 . 
     The operator may voluntarily tilt the deck  102  of the PT device  100  about the roll axis A 2  and the yaw axis A 3  to steer, e.g., control a direction of, the PT device  100  as the PT device is travelling as long as the operator&#39;s weight is distributed across the forefoot and heel of the operator&#39;s first foot  103 . The tilting of the deck  102  may be detected by various sensors (not shown) arranged in the deck  102 , e.g., coupled to a bottom surface of the deck  102  and configured to measure orientation information of the deck  102  (e.g., a gyroscope), movement of the PT device  100 , rotation of the wheel  130 , etc. The PT device  100  may also include various electrical components such as a power supply, a motor controller, a rider detection device, a power switch, a charge plug, illumination assemblies, etc. (not shown). 
     To provide information to the motor controller to control movement of the PT device  100  based on adjustment of the operator&#39;s weight on the first foot  103 , a rider detection device may be disposed in the first platform  110  of the PT device  100 . An example of a rider detection device  302  is shown in a perspective view  300  in  FIG. 3A  and in an exploded view  350  in  FIG. 3B . The rider detection device  302  may be a flat, rectangular panel coupled to an electrical connector  304  to electrically couple the rider detection device  302  to a motor controller configured with a microcontroller that receives information from sensor of a PT device and sends instructions to actuators of the PT device, such as the wheel  130  of  FIGS. 1, 2, and 16 . 
     The rider detection device  302  includes a deck portion  306 , which may be a rigid frame for the rider detection device  302 , and a pressure transducer  308  sandwiched between the deck portion  306 , the deck portion  306  arranged below the pressure transducer  308 , and a slip-resistant layer  310  arranged above the pressure transducer  308 , with respect to the y-axis. The exploded view  350  of  FIG. 3B  shows that the pressure transducer  308  is formed from several components. 
     The pressure transducer  308  includes an upper force-sensitive resistor (FSR) layer  312  and a lower conductive layer  314  separated by a spacer layer  316 . The FSR layer  312  may include any suitable layer having an electrical resistance that changes predictably in response to an applied force (e.g., a pressure exerted by an operator&#39;s foot placed on top of the rider detection device  302 ), such as a conductive polymer ink applied to a PET film substrate. The FSR layer  312  may be partially conductive and/or variably conductive with a variable resistance. The conductive layer  314  may include any suitable conductive material, such as a partial electrical circuit. 
     When the FSR layer  312  is displaced toward conductive layer  314  due to pressure applied by an operator&#39;s foot, the FSR layer  312  may contact the conductive layer  314 , completing the electrical circuit and transmitting a signal indicating that the operator is present. An amount of current flow induced by contact between the layers may be proportional to an amount of applied pressure, thus providing information about a desired speed of the PT device, for example. The conductive layer  314  is shown in  FIG. 3B  to include a portion that passes through an aperture  318  in the deck portion  306  to connect with the electrical connector  304 . 
     The spacer layer  316  may be formed from any suitable non-conductive, e.g., dielectric, material that maintains the FSR layer  312  and the conductive layer  314  separated without applied pressure. In some examples, as shown in  FIG. 3B , the spacer layer  316  includes a first portion  316   a  and a second portion  316   b  that may between placed adjacent to one another between the FSR layer  312  and the conductive layer  314 . Dimensions and shapes of the first portion  316   a  and second portion  316   a  of the spacer layer  316  may vary from the examples shown in  FIG. 3B . For example, the spacer layer  316  may be disposed along a periphery of the FSR layer  312  and conductive layer  314 , thereby leaving central or middle portions of each layer free to interact. 
     In some examples, the pressure transducer  308  may be divided into a first zone  320  and a second zone  322 , as shown in  FIG. 3A . The first zone  320  may correspond to a positioning of a first portion of the operator&#39;s lead foot, such as the forefoot, and the second zone  322  may correspond to a positioning of a second portion of the operator&#39;s lead foot, such as the heel. Detection of pressure in one zone but not the other may indicate a command to stop movement of the PT device. For example, when the operator raises the heel of the operator&#39;s lead foot off the rider detection device  302 , the microcontroller may instruct a hub motor of the PT device to decelerate and come to a full stop in response. 
     The slip-resistant layer  310  may be a layer positioned between the pressure transducer  308  and the operator&#39;s foot that provides traction for the operator&#39;s foot. For example, the slip-resistant layer  310  may include a non-skid material, grip tape, a textured layer, or any combination of such elements. The slip-resistant layer  310  may be similar in size or larger than the pressure transducer  308  such that the slip-resistant layer  310  also acts as a barrier between the pressure transducer and external objects, debris, liquids, etc. 
     While  FIG. 3B  shows a pressure transducer with a single conductive layer and FSR layer, other examples may include variations in quantities of each layer. For example, the pressure transducer may include two or more FSR layers and a suitable amount of spacer layers and conductive layers. Any suitable combination of layers may be utilized. 
     Displacement of the layers of the rider detection device  302  that allows a sensed force or pressure to be converted into an electrical signal may be relatively small. For example, deflection or displacement of the pressure transducer  308  may be in a range of 0.005 to 0.020 inches. In other words, a separation distance between the FSR layer  312  and the conductive layer  314  may be reduced by 0.005-0.020 inches when the operator applies an activation force or pressure to the rider detection device  302 . However, in other examples the displacement distance range may vary. In some examples, the rider detection device  302  may have a threshold, baseline amount of pressure to be placed upon the rider detection device  302  in order to activate the motor assembly of the PT device. Increasing a number of material layers between the operator&#39;s foot and the rider detection device  302  may desensitize the pressure transducer  308  to changes in pressure applied by the operator&#39;s foot. 
     For example, it may be desirable to add a concave curvature to a deck of the PT device. An increased thickness of the deck around a perimeter of the deck may impart the operator with greater control in maneuvering the PT device, increasing a responsive of the PT device to desired changes in direction as indicated by weight transfer through the operator&#39;s foot placed over the rider detection device  302 . However, forming the deck of the PT device with concave curvature may inhibit activation of the pressure transducer  308  by decreasing contact between the operator&#39;s foot and the rider detection device  302 . As an alternative, a footpad may be used that maintains sensitivity of the rider detection device  302  to changes in applied pressure while providing the operator with enhanced maneuverability of the PT device. 
     An example of a set of footpads  402  is shown in  FIG. 4  from a first perspective view  400 , in a birds-eye view  500  in  FIG. 5 , a profile view  600  in  FIG. 6 , a front view  700  in  FIG. 7 , and a second perspective view  800  in  FIG. 8 . A first cross-section  900  of the set of footpads  402  is depicted in  FIG. 9  and a second cross-section  1000  is illustrated in  FIG. 10 . As such,  FIGS. 4-10  are described collectively. 
     The set of footpads  402  includes a first pad  404  and a second pad  406 , each pad configured to couple to opposite ends of a PT device deck. For example, the first pad  404  may be coupled to an upper surface of the first platform  110  of  FIGS. 1 and 2 , and the second pad  406  may be coupled to an upper surface of the second platform  112  of  FIGS. 1 and 2 . The set of footpads  402  may be arranged sandwiched between the upper surfaces of the first platform and the second platform of the PT device deck and a layer of a textured material or non-slip layer, such as the first and second textured layers  126 ,  128  of  FIGS. 1 and 2  and the slip-resistant layer  310  of  FIGS. 3A-3B . As such, contact between an operator&#39;s feet and the textured, non-slip layer is maintained. 
     The first pad  404  and the second pad  406  may each have generally rectangular geometries, when viewed along the y-axis as shown in  FIG. 5 , two curved corners and at least one curved edge. For example, the first pad  404  may be arranged so that a first set of corners  408  that are rounded and a curved edge  410  are oriented towards a front end of the deck, e.g., the front end  122  of  FIGS. 1 and 2 . The curvature of the first set of corners  408  and the curved edge  410  may match a geometry of the first platform of the deck. The second pad  406  may be similarly shaped to match a geometry of the second platform of the deck. Dimensions of the first pad  404 , such as a width measured along the x-axis and a length measured along the z-axis may be similar to or smaller than dimensions of the first platform and dimensions of the second pad  406  may be similar to or smaller than dimensions of the second platform. 
     In the following paragraphs, details of the first pad  404  will be described and not the second pad  406  for brevity. However, aspects of the first pad  404  discussed below may be similarly applied to the second pad  406 . The curved edge  410  of the first pad  404  may be curved along the x-z plane, as illustrated in  FIG. 5 , curving outwards and away from a central region  412  of the first pad  404 . Side edges  414  of the first pad  404  may be straight or slightly curved, each side edge extending from one corner of the first set of corners  408  to a corner of a second set of corners  416 . The side edges  414  may include notches  403  proximate to the second set of corners  416  to allow access to screws disposed in the first platform. 
     The second set of corners  416  may form perpendicular corners with straight sides. An inner edge  418  of the first pad may be straight and parallel with the x-axis, extending between the second set of corners  416 . The first pad may include a flap  420  extending along the inner edge  418 , also between the second set of corners  416 . The flap  420  may extend along the z-axis away from the inner edge  418  and have a uniform length, the length measured along the z-axis. The flap  420  may be thinner than the first pad  404  between the inner edge  418  and the curved edge  410 , the thickness defined along the y-axis. 
     An upper surface  422  of the first pad  404  may be curved in a concave manner, e.g., curving downwards relative to the y-axis towards a bottom surface  424  of the first pad  404 , as depicted in  FIGS. 4, 6-10 . The bottom surface  424  may be straight and coplanar with the x-z plane. Due to the concave geometry of the upper surface  422 , the thickness of the first pad  404  (with the exception of the flap  420 ), may be thickest at an outer perimeter  425 , shown in  FIGS. 4 and 5 , of the first pad  404 , the outer perimeter  425  including the curved edge  410  and the side edges  414 . Furthermore, the thickness of the first pad  404  may be greatest at the first set of corners  408 , as shown in  FIGS. 6 and 7  and decrease between the first set of corners  408  along the curved edge  410  and along the side edges  414  between the first set of corners  408  and the second set of corners  416 . 
     With the exception of the flap  420 , the central region  412  of the first pad  404  may be a thinnest portion of the first pad  404 . The central region  412  may be biased towards the inner edge  418  so that a central portion of the inner edge  418 , indicated by a dashed line  426  in  FIG. 5 , is thinner than a central portion of the curved edge  410 , also indicated by a dashed line  428  in  FIG. 5 . Along the outer perimeter  425 , the upper surface  422  may curve continuously from the outer perimeter  425  to the central region  412 , the thickness of the first pad  404  gradually decreasing from the outer perimeter  425  to the central region  412 , as shown in  FIGS. 9 and 10 . 
     The first cross-section  900  of the first pad  404  of  FIG. 9  cuts the first pad  404  along the y-z plane and the second cross-section  1000  of  FIG. 10  cuts the first pad  404  along the x-y-plane. A thickness  902  of the central region  412  of the first pad  404  may be a portion of a thickness  904  of the first pad  404  at the first set of corners  408 , such as 20% or 30%, as shown in  FIG. 9 . In some examples, the thickness  902  of the central region  412  may be within a range of 20-60% of the thickness  904  of the first pad  404  at the first set of corners  408 . 
     The central region  412  of the first pad  404  may be elliptical in shape, when viewed from above, as shown in  FIG. 5 . A surface area of the central region  412  may form a portion of an overall surface area of the first pad  404 , such as 50%. In other examples, the central region  412  may form a portion of the overall surface area of the first pad  404  between 30%-70%. The first pad  404  may also include a cut-out  440 , as shown in  FIGS. 4, 5, 8 and 9 , extending entirely through the thickness of the first pad  404 , as shown in  FIG. 8 , to allow a logo disposed on the upper surface of the first platform to be visible through the first pad  404 . 
       FIGS. 6-10  shows that the bottom surface  424  of the first pad  404  is planar and not curved, allowing the bottom surface  424  to be in face-sharing contact with the upper surface of the first platform of the PT device across the entire bottom surface  424 . By configuring the first pad  404  with the central region  412  thinner than the outer perimeter  425  of the first pad  404 , the thinnest region of the first pad  404  may be positioned over a pressure transducer of the PT device, disposed in the first platform and directly below a central portion of the operator&#39;s lead foot. The reduced thickness of the first pad  404  at the central region  412  allows adjustments in weight transfer, through weight shifting on the lead foot, to transmit through the first pad  404  to the pressure transducer. 
     The thickness  902  of the central region  412  may be constrained to achieve a high degree of responsiveness of the pressure transducer to pressure changes. The thickness  904  of the first set of corners  408  and of the outer perimeter  425  of the first pad  404  may be more variable than the central region  412 , allowing the concavity of the first pad  404 , and thereby a receptiveness of the PT device to operator-induced steering, to be modified. For example, a first set of footpads  1400  is shown in  FIG. 14  and a second set of footpads  1500  is shown in  FIG. 15 . The first set of footpads  1400  may have a different thickness and concavity than the second set of footpads  1500 , as indicated by contours. 
     The first set of footpads  1400  of  FIG. 14  has a first pad  1401  and a second pad  1403 . The first pad  1401  may be configured to be applied to a portion of a deck of a PT device adapted with a pressure transducer. The first pad  1401  may have a first contour  1402 , indicating that an upper surface  1405  of the first set of footpads slopes upwards from the first contour  1402  to an outer perimeter  1404 , including a curved edge  1406  and side edges  1408 , of the first set of footpads  1400 . An increase in thickness, defined along the y-axis, from the first contour  1402  to the outer perimeter  1404  may be, as an example, 0.2 inches. Toes of an operator&#39;s lead foot may be positioned directly above and in contact with a region of the upper surface  1405  of the first pad  1401  between the first contour  1402  and one of the side edges  1408 . A heel of the operator&#39;s lead foot may be positioned directly above and in contact with a region the upper surface  1405  of the first pad between the first contour  1402  and the other of the side edges  1408 . By shifting the operator&#39;s weight towards the toes of the lead foot or towards the heel, the deck of the PT device may be tilted about a roll axis  1410  of the PT device. A concavity of the first set of footpads  1400  allows a smaller weight shift to effect an equal amount of tilting of the deck about the rolls axis  1410  compared to a set of footpads with a planar, e.g., not curved, upper surface. 
     The second set of footpads  1500  of  FIG. 15  has a first pad  1501  and a second pad  1503  which may be used similarly as the first set of footpads  1400 . The first pad  1501  may have a first contour  1502 , indicating that an upper surface  1505  of the second set of footpads  1500  slopes upwards from the first contour  1502  to second contour  1504 . An increase in thickness, defined along the y-axis, from the first contour  1502  to the second contour  1504  may be, in one example, similar to the increase in thickness in the first pad  1401  of the first set of footpads  1400  of 0.2 inches. An increase in thickness from the second contour  1504  to an outer perimeter  1506 , including a curved edge  1508  and side edges  1510 , may also be 0.2 inches. The increase in thickness from the first contour  1502  to the outer perimeter  1506  may therefore be 0.4 inches. The outer perimeter  1506  of the first pad  1501  of the second set of footpads  1500  may be twice as thick as the outer perimeter  1404  of the first pad  1401  of the first set of footpads  1400 . As such the second set of footpads  1500  may have a greater degree of concavity than the first set of footpads  1400 . The increased concave curvature of the second set of footpads  1500  may allow smaller weight shifts to effect equal tilting of the deck of the PT device about a roll axis  1512  compared to the first set of footpads  1400 . 
     As shown in a perspective view  1100  in  FIG. 11 , a set of concave footpads  1102  may be applied to a deck  1104  of a PT device  1106 . The set of concave footpads  1102  may be positioned over an upper surface of the deck  1104  where an operator&#39;s feet may be placed when standing on the deck  1104 . The set of concave footpads  1102  may be adhered to the upper surface of the deck  1104  by a layer of adhesive transfer tape. An example of a roll of adhesive transfer tape  1200  is shown in  FIG. 12 . The roll of adhesive transfer tape  1200  may have adhesive on both an upper surface and a bottom surface of the tape and may be cut to a desired shape to accommodate a geometry of the set of concave footpads  1102  of  FIG. 11 . 
     Returning to  FIG. 11 , a layer of a non-slip material, such as grip tape  1108 , may be applied to an upper surface of the set of concave footpads  1102 , between the set of concave footpads  1102  and the operator&#39;s feet. The grip tape  1108  provides a textured layer to increase traction between the soles of the operator&#39;s shoes and the set of concave footpads  1102 . An example of a roll of grip tape  1300  is shown in  FIG. 13 . The roll of grip tape  1300  may have a first surface  1302  that is textured and a second surface  1304 , opposite of the first surface  1302  that has a layer of an adhesive. 
     A layering of a concave footpad, similar to the set of footpads shown in  FIGS. 4-11 and 14-15 , on a deck of a PT device, is shown in an exploded view  1800  in  FIG. 18 . The exploded view  1800  includes the rider detection device  302  of  FIGS. 3A-3B  and further includes a concave footpad  1802 , positioned above, with respect to the y-axis, the rider detection device  302 . More specifically, a layer of adhesive  1804 , which may be a layer formed from the roll of adhesive transfer tape  1200  of  FIG. 12 , may be positioned between an upper face  1806  of the FSR layer  314  and a lower, planar surface  1808  of the concave footpad  1802 . The lower surface  1808  of the footpad  1802  may be coupled to the upper face  1806  of the FSR layer  314  by the layer of adhesive  1804 . An upper surface  1810  of the concave footpad  1802  is in face-sharing contact with a lower surface  1812  of a layer of grip tape  1814 . The lower surface  1812  of the layer of grip tape  1814  may have an adhesive coating to adhere to the upper surface  1810  of the concave footpad  1802  and an upper surface  1816  of the layer of grip tape  1814  may be textured and configured to directly contact a foot of an operator. Thus, pressure applied by the operator&#39;s foot is transmitted through the layers shown in  FIG. 18 , allowing the pressure transducer  308  to maintain sensitivity to variations in an applied downwards force. 
     A coupling of layers shown in  FIG. 18A  is shown stacked and in face-sharing contact in a cross-section  1850  depicted in  FIG. 18B , taken along line A-A′, along the y-x plane, shown in  FIG. 18A . The cross-section  1850  illustrates direct coupling of adjacent layers to one another, stacked along the y-axis. A difference between the curvatures of the lower surface  1808  of the footpad  1802  and the upper surface  1810  is shown. All layers below the footpad  1802  are planar while the layer of grip tape  1814  is curved similarly to the upper surface  1812  of the footpad  1802  due to the coupling of the layer of grip tape  1814  to the footpad  1802 . 
     A combination of one or more of a degree of concavity of an upper surface of a footpad, a planar bottom surface of the footpad, and a stiffness of the footpad (along with the corresponding geometry of the sensor, surrounding board, etc.) may together allow the footpad to be coupled to a pressure transducer of a PT device while maintaining a sensitivity of the pressure transducer across an entire surface area of the pressure transducer. The planarity of the bottom surface of the footpad enables directly coupling of the footpad across the entire surface area of a planar upper face of the pressure transducer. Application of a downwards mechanical force to any point along the surface area of the pressure transducer may be transmitted through the footpad to generate a current at the footpad, at a location corresponding to a location of the force. 
     However, imperfections in both the upper face of the pressure transducer and the bottom surface of the footpad may result in non-continuous contact across the surfaces of the pressure transducer and the footpad. For example, tiny bumps or udulations in the upper face of the pressure transducer may create points of contact (and non-contact) between the footpad and the pressure transducer surrounding by areas where the two components are spaced apart. A decrease in sensitivity due to the imperfections in the surfaces may be countered by providing the footpad with an amount of stiffness that balances sufficient rigidity of the footpad to support an operator&#39;s weight without permanent deformation with enough flexible to fill in areas around the tiny bumps in the upper face of the pressure transducer. Thus adjusting physical properties of the footpad may enable more continuous contact between the pressure transducer and the footpad. 
     For example, the footpad may be formed with a Shore A hardness of 90. By configuring the footpad with dimensions that at least cover the entire surface area of the pressure transducer and a target amount of concavity, such as the degree of concavity shown by the first set of footpads  1400  of  FIG. 14 , the footpad may be effectively coupled to the pressure transducer with a similar responsiveness to pressure changes as if the footpad were not arranged between the operator&#39;s foot and the pressure transducer. Varying the degree of concavity, e.g., to achieve a different reactivity to steering, may be accompanied by an adjustment to the stiffness of the footpad. As an example, imparting the footpad with more concavity may be balanced by a footpad with a lower durometer measurement. In another example, varying a thickness of a central region of the footpad, defined as a thinnest portion of the footpad, may include adjusting the stiffness of the footpad to maintain a sensitivity of the pressure transducer through the footpad. For example, a footpad with a thicker central region may be less stiff than a footpad with a thinner central region. 
     It will be appreciated that the examples of a set of footpads shown in  FIGS. 4-11, 14-15 , and  18  are non-limiting examples and variations to dimensions, geometry, thickness, placement on a deck of a PT device, notches, cut-outs, and number of footpads per PT device have been contemplated. Furthermore, while the example of a PT device shown in  FIGS. 2, 3, and 11  depict one type of PT device with a central wheel protruding through a deck, the set of footpads may be applied to many different types of PT devices, such as non-motorized skateboards, electric skateboards, snowboards, and various other types of devices configured to receive an operator&#39;s feet. In addition, relative thickness of the various elements coupled to the deck of the PT device, such as the layers shown in  FIGS. 18A-18B , and including the deck, may vary from the relative thicknesses shown. 
     Dimensions and a degree of concavity of a footpad or a set of footpads, e.g., the footpad of set of footpads  402  of  FIGS. 4-10, 1102  of  FIG. 11, 1400  of  FIG. 14, 1500  of  FIG. 15 , and  1802  of  FIG. 18 , for a PT device adapted with a pressure transducer in a deck of the PT device may be readily adjusted during a process for forming the se of footpads. The set of footpads may be formed from a flexible material, such as a rubber, that provides the set of footpads with a suitable amount of rigidity to resist permanent deformation and to transmit changes in pressure through a thickness of the set of footpads, as moderated by an operator&#39;s feet, balanced with an amount of cushioning to provide a comfortable positioning of the operator&#39;s feet on the set of footpads. For example, the set of footpads may be formed from polyurethane with a Shore A hardness of 90. In other examples, the set of footpads may be formed from a differ materials, such as agglomerated cork, foam, or mycelium. An example of a routine  1700  for forming the set of footpads is shown in  FIG. 17 . The routine  1700  may include a kit providing materials and instruments utilized during the routine which may be carried out by an operator. 
     At  1702 , the routine includes forming a mold for the set of footpads with a desired geometry for the set of footpads. The mold may be cut from wax, or formed from a rigid material such as plaster, concrete, or wood and sealed to impart the mold with smooth non-porous surfaces. Rubber is added to the mold at  1704 . Adding the rubber may include mixing reagents to form a liquid, pourable rubber at  1706 . For example, a volume of a polyurethane prepolymer, such as toluene diisocyanate, may be mixed with a volume of a polymerization agent, such as a blend of polyol and aromatic amines, in a predetermined ratio to achieve a desired hardness of the rubber. A tint or dye may be added to the liquid rubber at  1708  to impart the rubber with a desired color. At  1710 , the routine may include pouring the liquid rubber into the mold to fill cavities of the mold. 
     At  1712 , the method includes allowing a predetermined period of time to elapse to enable curing of the liquid rubber. During curing, the reagents may interact and induce polymerization and causing a phase change of the rubber, from liquid to solid. The cured, solid set of footpads are removed from the mold at  1714 . The finished set of footpads may then be adhered to a deck of the PT device with transfer tape, such as the roll of transfer tape  1200  shown in  FIG. 12 , and topped with grip tape, such as the roll of grip tape  1300  shown in  FIG. 13 . 
     In some examples, the kit may also include a tool or instruments for preparing the deck of the PT device to receive the set of footpads. For examples, the deck may have a layer of grip tape directly coupled to an upper surface of the deck. It may be desirable to remove the grip tape prior to application of the set of foot pads. 
     In this way, a set of footpads may be added to a deck of a personal transport device, such as a motorized skateboard, to provide a concave curvature without adversely affecting efficiency of a pressure transducer disposed in the deck. The concave curvature may increase a responsiveness of the personal transport device to rocking motions across an operator&#39;s feet, when the operator is standing on the set of footpads, to effect changes in direction of the device when the device is in motion. The pressure transducer in the deck detects changes in pressure, transmitted through the operator&#39;s feet, across a surface of the pressure transducer and adjusts a speed of the personal transport device in response. By configuring each pad of the set of footpads with a central region that is thinner than a peripheral region of each pad and forming the set of footpads from a material with a specific balance of rigidity and cushioning, sensitivity of the pressure transducer to changes in pressure is maintained in spite of the distancing of an operator&#39;s foot from the pressure transducer by the thickness of the central region of the pad. The set of footpads are manufactured via a low cost method that allows dimensions and a degree of curvature of the footpads to be readily adjusted thereby enabling modification of the set of footpads according to operator&#39;s preferences and configuration of the personal transport device. 
     A technical effect of implementing the set of footpads in a personal transport device is that a steering efficiency of the device is increased while a sensitivity of the pressure transducer to changes in applied force is maintained. 
     The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.