Source: http://www.google.com/patents/US20050029029?dq=system+for+measuring+web+traffic&ei=Lg8FT__TIIr-sQKzxaGRCg
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Matched Legal Cases: ['art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'art 20', 'arts 20', 'arts 10', 'arts 20', 'arts 20', 'arts 20']

Patent US20050029029 - Robotic cart pulling vehicle - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA robotic cart pulling vehicle includes a positioning error reducing system for reducing accumulated error in the ded-reckoning navigational system. The positioning error reducing system including at least one of a low load transfer point of the cart attaching mechanism, a floor variation compliance...http://www.google.com/patents/US20050029029?utm_source=gb-gplus-sharePatent US20050029029 - Robotic cart pulling vehicleAdvanced Patent SearchPublication numberUS20050029029 A1Publication typeApplicationApplication numberUS 10/651,497Publication dateFeb 10, 2005Filing dateAug 29, 2003Priority dateAug 30, 2002Also published asEP1587725A2, EP1587725A4, EP1587725B1, US7100725, US7431115, US8041455, US20070051546, US20090030569, WO2004020267A2, WO2004020267A3Publication number10651497, 651497, US 2005/0029029 A1, US 2005/029029 A1, US 20050029029 A1, US 20050029029A1, US 2005029029 A1, US 2005029029A1, US-A1-20050029029, US-A1-2005029029, US2005/0029029A1, US2005/029029A1, US20050029029 A1, US20050029029A1, US2005029029 A1, US2005029029A1InventorsHenry ThorneOriginal AssigneeAethon, Inc.Export CitationBiBTeX, EndNote, RefManReferenced by (9), Classifications (13), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetRobotic cart pulling vehicleUS 20050029029 A1Abstract A robotic cart pulling vehicle includes a positioning error reducing system for reducing accumulated error in the ded-reckoning navigational system. The positioning error reducing system including at least one of a low load transfer point of the cart attaching mechanism, a floor variation compliance structure whereby the drive wheels maintain a substantially even distribution of load over minor surface variations, a minimal wheel contact surface structure, a calibration structure using at least one proximity sensor mounted on the robot body, and a common electrical and mechanical connection between the cart and the robot vehicle formed by a cart attaching post. Images(7) Claims(20)
The ultimate goal in addressing this issue may be some external system that keeps track of where the robotic vehicle is and which way it's facing and keeps the robotic vehicle informed. GPS is close to this goal, but it doesn't tell the robotic vehicle which way it's facing, it only works outside, and it isn't accurate enough to guide a robotic vehicle through a doorway. In lieu of this ideal system, some robots instead guess where they are from the amount they've turned each wheel. It's called ded-reckoning. This method is inherently flawed; therefore many robotic vehicles using deduced reckoning then correct any error that accumulates with any of a wide variety of sensor methods. Most research effort is focused on the sensors for correcting the ded-reckoning error. One advance in the field with the present invention is to instead focus on the cause of the errors and the minimization and/or elimination of them. The present methods employed in the instant invention reduce ded-reckoning error from a typical 7% found in prior art robotic robots using deduced reckoning to less than 1% in the present invention. Lateral accuracy in the known robotic vehicle position is hard to achieve because it depends on accurate knowledge of the heading of the robotic vehicle. If the robotic vehicle heading is just 6 degrees off (i.e. 6 degrees difference between the actual heading and the estimated heading assumed by the vehicle), traveling 10 feet forward will result in a lateral error of 1 foot. The robotic vehicle is 1 foot away from where it believes that it is, with the errors continuing to compound until corrected. The key to the effectiveness of any ded-reckoning system is maintaining the heading information as accurately as possible. Typical robot systems accumulate 10 to 16 degrees of heading error in executing a 180 degree rotation; the present robotic vehicle generates only 2.5 degrees of error executing a 180 degree rotation. As discussed above, ded-reckoning systems accumulate error no matter how well they are designed and the present system still accumulates some small amount of error. The present invention incorporates a system for zeroing out accumulated error that utilize pre established checkpoints and may be referred to as light whisker� checkpoints. A map of the world is held internally by the robotic vehicle 10 as understood by those in the art. On this map, virtual light whisker� checkpoints� (LWC) are positioned along walls that have straight sections longer than a predetermined minimum amount, such as 2 feet. As many LWC's as can fit are placed along any wall that meets the minimum (e.g. 2′) straight section requirement. When the robotic vehicle 10 is traveling parallel to a wall with a LWC, a conventional range sensor 27, such as a Sharp GP2D12 infrared sensor, is used to look sideways at the wall and measure a series of distances to the wall. FIG. 11 illustrates the Sharp GP2D12 sensor 27 which is described as providing less influence on the color of reflected objects, reflectivity. With the sensor 27, an external control circuit is unnecessary and the sensor 27 is very low cost. The GP2D12O infrared sensor 27 has special lenses and takes a continuous distance reading and reports the distance as an analog voltage with a distance range of 4 cm to 30 cm. The interface is 3-wire with power, ground and the output voltage and requires a JST 3-pin connector 29 that is shown in FIG. 11. The measurements from the sensor 27 are provided to the controller 16 times a second as the robotic vehicle 10 travels. The sensor 27 reports the distance as an analog signal accurate to ⅕″ and this is utilized, combined with the known geometry of the sensor 27 on the robotic vehicle 10 to determine a sequence of positions relative to the robot based coordinate system where this wall should be. Using this set of positions, a statistical method (to eliminate anomalous readings) may be used to determine if the data meets the criterion for a wall (e.g. �this section should be straight�). Then the following is determined: 1) the distance over to the wall and 2) the orientation of the wall. This orientation is compared to the expected orientation of the wall knowing where the robotic vehicle 10 believes it is with respect to its internal map. If the calculated position of the wall appears to be radically different from the previous expected position it is assumed a measurement error occurred and the data can be rejected. The value of what is �radically different� can be selected as known in the art. If the correction is within reason, it is assumed that the sensor data is right and the robotic vehicle's ded-reckoning based assumption about the position is not, and the new orientation is used to update the assumption about the vehicle position and orientation within the map (i.e. the robot's assumed orientation is calibrated). An additional feature maybe added where the vehicle 10 also �looks� at the ending or start of the wall to determine the other offset, (e.g. the forward/backward position). Again, the robotic vehicle 10 will do this as often as possible, sometimes every ten feet. This method may be modified to be used on non-linear continuous surfaces as well. For example, the checkpoints may be positioned on a wall having a known radius of curvature. Additionally, it is important to note that the checkpoints represent positions on a given wall, but no physical modification of the existing wall is required for utilizing the present invention. In this respect the checkpoints may be considered to be virtual checkpoints. A key feature is the fact that the robotic vehicle 10 is mainly measuring orientation error and the fact that there are discrete measuring places or �checkpoints� that are �set up� then used comparatively. The use of a range sensor 27 is very effective for picking up orientation error with relatively little a sensor investment. The use of an electrical connection through the mechanical connection of the cart attaching mechanism 24 between cart 20 and robot or robotic vehicle 10 is another key feature of the positioning error reducing system for reducing accumulated error in the ded-reckoning navigational system according to the present invention. This connection allows for the passage of both information and power between the cart 20 and the robot 10 as well as the transferring of the mechanical forces for towing of the cart 20. The robot 10 needs both a mechanical connection to the cart 20 that it is pulling and an electrical connection if the cart 20 is to include any input or output devices associated with the robot 10. These can include directional controls (e.g. a joystick controller for movement) for controlling movement of the robot 10, sensors for assisting in detecting obstacles or position, emergency override (e.g. a stop button), a standard computer of touch screen interface, audible or visual indicators (e.g. light and sound systems), supplemental battery power for the robot 10, or the like. The electrical connection has two purposes, one to pass information back and forth between processors in each device, and the other to pass power in the case where the battery for driving the robot motors 30 is located in the cart 20 not the robot 10. For this purpose the present invention provides a novel connector that takes advantage of the mechanical loads to create excellent electrical current carrying capacity all through the same device. Essentially, there are two loads exerted on the robot 10 by the cart 20, one is downward where the robot 10 is holding up at least half of the cart 20, and the other is lateral, the one that actually pulls the cart 20 along. The downward load on the robot 10 is supported by one electrical connection and the lateral is supported by the return electrical connection. In this way, the invention can pass up to 20 amps of current through the connection while maintaining strong enough surface contact to avoid any arcing that would eventually wear the materials out. This method has the benefit of not only maintaining great contact but it also keeps the two electrical poles mechanically isolated from each other because they are in different planes. Standard ring approaches always have potential shorting problems during insertion and removal of the post into the connector while this method eliminates this problem. The details of this arrangement are found in FIGS. 8 a, 9 a and 10. One electrical connection between the cart 20 and the robot 10 is made between a bolt 42 at the end of wagon or cart attaching post 44 and the receiving metal support 46 on the robot 10 in a bore within the robot body and housing. The weight of the cart 20 that is carried by the robot 10 maintains this connection. This weight should be at least half of the weight of the cart 20, since increased weight on the robot 10 reduces accumulating positioning error due to a reduction in wheel slippage. The second electrical connection is between the steel tube 48 of the post and a brass bushing 50 in the robot 10. The tight fit between the tube 48 and the bushing 50 and the forces exerted through pulling of the cart 20 maintain this electrical connection. FIGS. 8 b and 9 b illustrate an alternative construction of the post 44 which still provides for both a mechanical and an electrical connection between the robotic vehicle 10 and the cart 20. This embodiment will avoid problems than can be encountered with a mechanical connection between the bolt 42 and the metal support 46 due to high loading. Specifically the post 44 includes a thrust bearing 142 at the end of the tube 48 in the bushing 50 which serves as the load transfer point between the cart 20 and the robot vehicle 10. A bearing sleeve 144 is in the bushing 50 between the tube 48 and the bushing 50 to allow free rotation of between the robot vehicle 10 and the cart 20 (and the cart attaching post 44 which is secured thereto through the post connector flange 145). Three copper rings 146 are surrounding the tube 48, insulated from each other and the tube 48. A brush contact 148 is biased into contact with a selected copper ring 144 by a steel spring support 150 attached to the body 12 through an upper or lower post support member 152 and 154 respectively. The upper and lower post support 152 and 154 may be considered to define a bore in the body 12 for the post 44. Another brush contact 148 may be biased against the tube 48 to provide a ground contact. The copper rings 148 and the brush contacts which engage them form a slip ring type electrical connection for electrically coupling the robotic vehicle 20 with the cart 20 (wires from the brush contacts to the controller 16 and from the cart 20 through the tube 48 to the rings 146 are not shown). Additional copper ring 148 and brush contacts 148 may be added if additional electrical connections are desired. The use of the central post 44 will avoid the positioning errors that can be introduced with a separate electrical and mechanical connection. For example a separate electrical cord between the cart 20 and the robot 10 may wrap around a mechanical connection as the robot turns relative to the cart 20 eventually restricting further rotational movement there between and creating large positional errors. Another key feature of the positioning error reducing system for reducing accumulated error in the ded-reckoning navigational system according to the present invention is the use of the mechanical/electrical connection between cart 20 and robot 10 that is rigid front to back but allows a certain amount side to side rotation, such as three degrees, forming a floor variation compliance structure. In this regard the connection 24 above the bushing 50 will be an ellipse or elongated along the vehicle wheel axis such as in the upper post support 152. The ellipse or elongation is along the wheel axles. This compliance is shown in FIG. 7 through the tilting of the post 44 relative to the robot 10, whereby each drive wheel 14 is mounted to said robot body 12 in a manner allowing vertical movement of said wheel 14 relative to the cart attaching post 44 in the amount of at least three degrees measured from a center point of the collinear drive wheel axles. In this manner the collinear drive wheels 14 maintain a substantially even distribution of load over minor surface variations. There is always some amount of slippage occurring between the wheels 14 and the floor. The present robot 10 is of the two wheeled counter-rotating type and any heading change is calculated by knowing how much more one wheel 14 has turned than another. Slippage is difficult to measure. If the robot 10 could measure it, then it could calculate the impact on the heading by knowing how much more one wheel 14 has slipped than the other, which is described in some of the prior art patents. The present strategy is to instead try to keep the slippage minimal and equal between the wheels 14 by using the following methods: a) to minimize the slippage on smooth surface floors the robot 10 uses urethane coating 54 (such as on in line skate wheels) on the wheels 14 which has an incredibly large coefficient of friction while also being extremely durable; b) the wagon or cart 20 is attached to the robot 10 in the center between the wheels 14 through a near frictionless bearing (i.e. the post 44 can rotate in the attaching mechanism 24) which keeps the lateral forces equal between the wheels 14; c) the wagon or cart 20 is attached to the robot 10 (i.e. the cart loading forces are transferred) as low as possible to maintain the cart load as low as possible on the robot 10 (the forces being transferred through the bushing 50) which has the effect of keeping the downward forces as even as possible because the wagon or cart 20 isn't attempting to tip the robot 10 over as it is pulled around corners (this is believed to be the source of the greatest orientation error accumulation); d) the robot 10 is designed to put as much of the weight of its cargo (the wagon or cart 20) over the robot 10 as possible; e) finally the robot 10 is designed to reduce the rolling resistance and keeping the accelerations low. As discussed above, the swivel or cart attaching mechanism 24 for the robot 10 has compliance of plus and minus three degrees about a vector pointing in the forward travel direction of the robot 10. In other words the post 44 can pivot in a plane defined by the wheel 14 axles. This compliance allows the robot 10 to have one wheel 14 a half inch higher than the other wheel 14 while still distributing the loads nearly evenly between them. This compensates for unevenness of the floor, which in a perfectly stiff connection (i.e. no compliance) could shift all the load to a single wheel 10 like a car with three wheels on the curb and the fourth hanging off over the curb. This is especially critical in navigating over door jambs which can be a half inch high where the robot 10 could cross them at a diagonal essentially leaving one wheel 14 completely off the floor without this feature. This side to side swivel is a key feature of the present invention, and the lack of which causes other robots to not work. There are two reasons: 1) floors not being perfectly level (in fact, it has been observed that variations of 20″ side to side often exist when traveling straight forward 15 feet); and 2) when turning, the centripetal force of the robot and cart places more load on the outside wheel than the inside wheel if this swivel is not present and this would cause significant error. The only way this is solved is putting the attachment low (i.e. the position of the load transferring bushing 50) and with swivel about a forward pointing axis. Otherwise, there are times when all the weight would be on one wheel 14 and the creep that occurs between the floor and the tread would be drastically uneven causing large errors. Additionally, to keep the slip equal between the wheels 14 the invention essentially uses a strategy of keeping the forces equal between them. Slippage is proportional to lateral forces (forces in the plane of the floor Fl) and inversely proportional to the downward force (Fd) the good force which maintains the friction between the wheel. There is also a random slippage caused by things like dirt on the floor that we call F (random noise) and over which there is no control. Slippage=K(Fl/Fdx)�(F(random noise)) To minimize the slippage the robot 10 is designed to increase Fd as much as possible by putting as much of the weight of its cargo over the robot 10 as practical. The robot 10 design also tries to minimize Fl by reducing the rolling resistance and keeping the accelerations low. The trickier part is that the design of the robot 10 also tries to keep Fl and Fd as close to the same on each the left and right wheel 14 as possible so that on average (not constantly because there is still the random element which is inconsistent between the wheels 14) but on average, the slip that does occur is the same on both wheels 14 so that although there is some positional error generated, the heading error accumulation is minimal. The robot 10 design does this by not only attaching the cart 20 in the center between the wheels 14 through a near frictionless bearing 144 which keeps the lateral forces equal between the wheels 10 but the invention also attaches the cart load as low as possible on the robot 10 which has the effect of keeping the downward forces as even as possible because the cart 20 isn't attempting to tip the robot 10 over as it is pulled around corners, the source of the greatest orientation error accumulation. The load transfer point between the post and the robot 10 (i.e. the bushing 50) is below the wheel axle. More significantly the height of the load transfer point is less than ⅕ and preferably less than {fraction (1/10)} of the wheel base. The robotic vehicle 10 of the present invention provides a number of unique designs for the wheels 14 as shown in FIGS. 5, 6 a and 6 b. Regarding the wheel design, the sticky urethane, or polyurethane, coating tread being provided as thin as possible over the hardened annular disk 60 will minimize the wheel radius variation. The radius variation of the wheel 14 is due to compression of the urethane coating. In the present invention the thin coating of urethane is selected such that the compression of the wheels 14 under load (i.e. the change in radius of the wheel due to compression of the urethane coating) is less than 2% of the wheel radius, and preferably less than 1% of the wheel radius. The load referred to is more precisely the change in load between a robot and attached unloaded cart and the robot and attached loaded cart. The robot 10 and attached unloaded cart 20 are considered a base line, or unloaded, state for the wheels 14. This is in contrast to prior art dirigible wheels that compress, in operation, to a large fraction of the wheel radius, resulting in significant deduced reckoning error. Additionally, the annular wheel contact patch is provided as narrow as possible, on the order of 0.20 in, to keep the effective width between the wheels 14 as constant as possible. A large contact patch for the wheels will result in a variation of the effective wheel base. In the present invention the width of the contact patch of each wheel 14 is less than 1.5%, and preferably less than 1% of the wheel base between the wheels. The narrow wheels allow the variations in the effective wheel base to remain relatively small, specifically the change in the wheel base of the the robot 10 will be less than 2%, possibly even less than 0.5%. These wheel design features minimize deduced reckoning error as discussed above. Additionally, the system of the present invention is designed to provide the cargo weight mainly over the robot 10 to maximize traction and minimize wheel slippage, minimizing wheel error. Furthermore, the attachment of the cart load as low as possible will keep the downward force as even as possible so that the cart is not attempting to tip the robot over as being pulled around corners, as discussed above. All of these design considerations improve the deduced reckoning of the present invention. The robotic vehicle 10 of the present invention provides an automatic, labor-saving indoor freight hauler that is capable of hauling up to 500 pounds of goods on a cart 20 and can fit into a suitcase. The robotic vehicle 10 is generally the size of a suit box, about 20 inches wide and 8 inches tall. The vehicle 10 can effectively be described as a circuit board on wheels 14 mounted on a metal chassis or body 12 with a set of batteries 18, a PC mother board and with attached sensors 27, 28. The described vehicle 10 can perform rounds stopping at a series of stations or can do fetch and deliver errands and can haul a variety of carts 20 to the appropriate job. It is anticipated that the robotic vehicle 10 will be controlled with a graphical user interface. Furthermore, the carts 10 can be modified to include the battery as discussed above, or other interface connections such as a steerable joystick and the like. Another key feature of the present invention is the ability to easily retrofit existing carts 20 to be utilized with the robot 10 of the present invention. The retrofitting of existing carts 20 would generally only require the addition of an appropriate post 44. Additional elements such as supplemental batteries, input devices such as steering joystick or a keyboard, or sensors may also be retrofitted onto the existing carts 20. The above described embodiments is intended to be merely illustrative of the present invention and not restrictive thereof. A wide number of modifications are anticipated within the scope of the present invention as will be appreciated by those of ordinary skill in the art. The scope of the present invention is intended to be defined by the appended claims and equivalents thereof. Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7894939May 24, 2010Feb 22, 2011Aethon, Inc.Robotic ordering and delivery apparatuses, systems and methodsUS7996109Oct 16, 2006Aug 9, 2011Aethon, Inc.Robotic ordering and delivery apparatuses, systems and methodsUS8010230May 24, 2010Aug 30, 2011Aethon, Inc.Robotic ordering and delivery apparatuses, systems and methodsUS8204624Feb 15, 2011Jun 19, 2012Aethon, Inc.Robotic ordering and delivery apparatuses, systems and methodsUS8483876 *Nov 13, 2008Jul 9, 2013Honda Motor Co., Ltd.Controller of mobile robotUS20080277391 *May 7, 2007Nov 13, 2008International Business Machines CorporationMobile, Robotic CrateUS20100268382 *Nov 13, 2008Oct 21, 2010Honda Motor Co., Ltd.Controller of mobile robotUS20110271469 *Feb 8, 2011Nov 10, 2011Andrew ZieglerAutonomous surface cleaning robot for wet and dry cleaningUS20120185122 *Dec 15, 2011Jul 19, 2012Casepick Systems, LlcBot having high speed stability* Cited by examinerClassifications U.S. Classification180/167International ClassificationB62D1/00, B62D, B62D1/24, G05D1/02Cooperative ClassificationG05D2201/0206, G05D2201/0211, G05D1/0274, G05D1/0272, G05D1/0242European ClassificationG05D1/02E14M, G05D1/02E14D, G05D1/02E6NLegal EventsDateCodeEventDescriptionDec 21, 2009FPAYFee paymentYear of fee payment: 4Mar 5, 2004ASAssignmentOwner name: AETHON INCORPORATED, PENNSYLVANIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:THORNE, HENRY F.;REEL/FRAME:014401/0949Effective date: 20030823RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google