CA2138104A1 - Storage and retrieval machine including overweight detection - Google Patents
Storage and retrieval machine including overweight detectionInfo
- Publication number
- CA2138104A1 CA2138104A1 CA 2138104 CA2138104A CA2138104A1 CA 2138104 A1 CA2138104 A1 CA 2138104A1 CA 2138104 CA2138104 CA 2138104 CA 2138104 A CA2138104 A CA 2138104A CA 2138104 A1 CA2138104 A1 CA 2138104A1
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- Prior art keywords
- carriage
- storage
- motor
- control system
- load
- Prior art date
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Abstract
A storage and retrieval machine having a base movable in opposite horizontal directions, a mast mounted on the base, and a carriage movable in opposite vertical directions on the mast. The carriage is capable of supporting a load. A motor and a motor servo are provided for moving the carriage in its opposite vertical directions. An analog signal is taken from the motor servo which is proportional to the load on the motor. This signal is compared to a predetermined threshold value to determine if the load is overweight.
Description
2~3~10~
`~, H1~19063 STORAGE AND RETRIEVAL M~C~TN~
INCLUDING OVERWEIGHT DETECTION
FIELD OF THE INVENTION
The invention relates generally to storage and retrieval machines.
BACKGROUND OF THE INVENTION
Storage and retrieval machines are devices which include a horizontally moveable base, a mast mounted on and extending vertically from the base, a vertically moveable carriage supported by the mast, and a horizontally moveable shuttle, capable of engaging or releasing an object, supported by the carriage. A remote control source gives a comm~n~ to control means on-board the storage and retrieval machine to move the carriage to a particular storage location and either deliver or retrieve an object at the storage location. Either the remote control source or the on-board control means provides specific instructions for movement of the base, the carriage and the shuttle of the storage and retrieval machine. The movement instructions are utilized by further control and/or drive means to operate the ~381 0~
-HE~19063 base, carriage and shuttle to the necessary locations. The movement instructions include, e.g., distance to move or location to move to, maximum velocity, acceleration rate and deceleration rate, for both the base and the carriage.
A typical storage and retrieval machine is capable of handling loads of varying weights.
Examples of storage and retrieval machines are disclosed in U.S. Patent No. 5,170,863 and in U.S.
Patent Application Serial No. 08/042,241, both of which are assigned to the assignee of the present invention and both of which are incorporated herein by reference.
SUMMARY OF THE INVENTION
The invention provides a storage and retrieval machine including a base movable in opposite horizontal directions, a mast mounted on the base, a carriage movable in opposite vertical directions on the mast and capable of carrying a load, and a control system, the control system providing overweight detection for ensuring that the weight of a load picked up by the storage and retrieval machine ~13810~
-H~19063 is not greater than the capacity of the storage and retrieval machine. Motors and motor servos are also provided for moving the base and carriage in their respective opposite horizontal directions or opposite vertical directions. A tension member, such as a rope, belt, chain, etc., is connected to the carriage, is reeved about an upper pulley or sheave, and is engaged by a motor to vertically move the carriage.
One method of ensuring that the weight of the load is not greater than the capacity of the storage and retrieval machine involves using a load cell or strain gauge on the tension member. A problem with this is that it is very expensive.
The inventors of the present invention have recognized that the weight of the load on the carriage puts a tension on the tension member, which tension is directly proportional to the weight of the load. The tension on the tension member results in a load being placed on the motor. The power supplied to the motor to support the load is directly proportional to the weight of the load. The motor servo has an analog current feedback output which ~381b~
'_ H1~19063 provides a signal indicative of power supplied to the motor and which is connected to the control system via an analog-to-digital converter. The analog-to-digital converter converts the signal from the current feedback output of the motor servo to a digital representation. The control system compares this digital representation from the analog-to-digital converter to a predetermined threshold value and, if the digital representation is greater than the predetermined threshold value, the control system provides an error signal indicating that the load is overweight.
In one embodiment of the invention, after the carriage picks up a load, the control system disables the motor servo for a predetermined amount of time, stopping vertical movement of the carriage for a predetermined amount of time before the determination is made as to whether or not the load is overweight.
This allows the load to stabilize before the determination is made as to whether or not the load is overweight.
The invention provides a low cost and simple system for ensuring that the weight of a load picked Z13811~
-up by the storage and retrieval machine is not greater than the capacity of the storage and retrieval machine. Thus, damage to the storage and retrieval machine is avoided.
Other features and advantages of the invention will become apparent to those of ordinary skill in the art upon review of the following detailed description, claims, and drawings.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side elevation view of a storage and retrieval machine incorporating the present invention;
Fig. 2 is a front elevation view of the storage and retrieval machine illustrated in Fig. 1; and Fig. 3 is a schematic circuit diagram for the storage and retrieval machine shown in Figs. 1 and 2 in which the present invention is incorporated.
Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or ~381~4 _ HE~19063 illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
DETAILED DESCRIPTION OF THE
PREFERRED EM~30DIMENT OF THE INVENTION
Shown in Figs. 1-2 of the drawings is a storage and retrieval machine, which is also referred to herein as an SRM. The storage and retrieval machine has a base 2, a mast 4 mounted on and extending upwardly from the base, a carriage 6 movable vertically on a path along the length of the mast 4 to selected vertical locations, a shuttle 8 that is mounted on the carriage 6 for generally horizontal movement and that is capable of picking up and releasing loads, a base and carriage drive means 10 and a control system 12 (Figs. 1 and 3). The base 2 has (see Fig. 1) a length 37 including opposite ends 36 and 38. A drive wheel 28 rotating about an axis 50 and an idler wheel 30 rotating about an axis 56 comprise part of the drive means 10 and are ` ~1381~4 .~
H~19063 respectively mounted on the ends 36 and 38 of the base 2 and roll along a rail 24 supported on a foundation 26 and running through an aisle path 22.
The aisle path 22 extends through a storage area such as a warehouse having stacked storage racks 20.
Upper guide wheels 32 on the mast 4 engage a guide rail 34 to guide the SRM along the rail 24 and maintain the machine in an upright position.
The drive means 10 also includes a base drive 14 controlling a motor 40. The motor 40 is connected to and drives the drive wheel 28 so that the base 2 and thereby the SRM travel in selected opposite directions horizontally and in the direction of the length of the base along the rail 24 to selected locations in the aisle path 22 adjacent to the stacked storage racks 20. At each aisle location of the SRM, the carriage 6 is driven in one of opposite vertical directions to a selected one of the storage racks 20 where the shuttle 8 is driven generally horizontally and in directions transverse to the aisle path 22 into a storage rack to deliver or retrieve a load object such as box 44 carried on the shuttle as shown in Figs. 1 and 2.
21381û4 The drive means 10 further includes (see Fig. 3) a carriage drive servo 16, having an analog output 200. The drive means 10 further includes (see Figs.
1 and 3) a carriage motor 42. The carriage motor 42 is controlled by the carriage drive servo 16 and is connected to and acts through a drum assembly 82 (Fig. 1) to drive the carriage 6. While other motor servos could be employed, in the illustrated embodiment of the invention, the carriage drive servo 16 is an Indramat servo amplifier #KDS 1.1-150-300 W1/220, and has an analog output 200 providing 50mV
per Amp, with a range of zero to five Volts DC. The motor 42 and the drum assembly 82 are both mounted on a frame 46 (Fig. 1) which comprises part of the base 2. The motor 42 drives the drum assembly 82, and thereby extends or retracts a tension member 48 which is part of the assembly 82, and which is reeved over a sheave or pulley 52 on the mast 4 and is connected to the carriage 6. The tension member 48 can be a rope, a chain, a belt, or any other suitable flexible member. A cabinet 54 is also mounted on the base 2 for enclosing a portion of the components of the control system 12. Suitable means (not shown) is 810~
~.
~ 19063 provided for supplying electrical power for the various drives and the control system 12 of the SRM
described hereinafter.
The carriage 6 includes (see Fig. 2) a frame 60 upon which the shuttle 8 is mounted and to which is connected the tension member 48 for moving the carriage 6 vertically along the mast 4 in response to the operation of the carriage motor 42 and the drum assembly 82. The carriage 6 is movably supported and guided on the mast 4 by means of upper support rollers 62, 64 and 66, 68 rotatably mounted on an upper section 70 of the frame 60, and by means of lower support rollers 72, 74, and 76, 78 rotatably mounted on a lower section 80 of the frame 60.
The shuttle 8 comprises a shuttle drive means 90 (Fig. 1) mounted on the lower section 80 of the carriage frame 60, a lower base plate 92 (Fig. 2) also mounted on the lower frame section 80, an intermediate plate 94 (Fig. 1), a top plate 96, and a shuttle telescoping drive 100. Operation of the shuttle telescoping drive 100 by the shuttle drive means 90 causes the plates 94 and 96 to extend in a telescoping fashion to the position shown in Fig. 2 ~138104 -H1~19063 and retract to a centered position on the lower frame section 80. The shuttle 8 thus operates in conjunction with the base 2 and carriage 6 to deposit the load 44 in or retract the load 44 from a storage rack 20.
The control system 12 is illustrated in greater detail in Fig. 3 and includes: a supervisory control means 110 which receives operating comm~n~
information on lines 88 from a remote computer 18; a base control means 120 for controlling the movement of the base 2 of the SRM along a path of travel in the aisle path 22; a carriage control means 130 for controlling the movement of the carriage 6 along a path of travel on the mast 4; and a shuttle control means 140 for controlling the extending and retracting movement of the shuttle 8 into and out of a storage rack 20. The supervisory control means 110 has connections to the base control means 120, the carriage control means 130 and the shuttle control means 140 respectively represented by lines 112, 114 and 116.
The SRM includes (see Fig. 3) a distance meter 102 connected by a line 104 to the base control means ~3~1~4 ~19063 120, a reflector 98 located at the end of the aisle path 22, and a proximity photocell 106 connected to the supervisory control means 110 by a line 108. The SRM also includes a carriage encoder 136 connected to the control means 130 by a line 138, and a home switch 134 connected to the carriage control means 130 by a line 118. Other means of determ-n'ng and controlling the position of the base 2, shuttle 8, and carriage 6 may be employed.
The supervisory control means 110 may comprise, for example, a programmable logic controller (PLC) which is programmed to produce specific operating instructions to the base control means 120, the carriage control means 130 and the shuttle control means 140 in response to the operating comm~n~ from the remote computer 18. While other PLCs may be employed, in the illustrated embodiment the PLC is an Allen-Bradley PLC 5/20 #1785-120B. The operating information from the remote computer 18 is normally a comm~n~ to pick up or deposit a load object 44 or to move to a specified location. The information from the remote computer 18 is converted to RS232C format form and is then converted to a memory block of ASCII
~138104 -H1~19063 characters in binary code form at an input module of the supervisory control means 110. The supervisory control means 110 also has various discrete inputs for receiving operating condition indications relating to the base 2, carriage 6 and shuttle 8 and their associated controls. These include an input on the line 108 from the proximity photocell 106 indicating the location of the base 2 along the aisle path 22, an input on line 118 from the home switch 134 indicating if the carriage 6 is at its reference home position, and inputs (not shown) indicating the position of and the full or empty condition of the shuttle. The supervisory control means 110 produces control instructions in response to not only the operating comm~n~ received from the remote computer 18, but also in accord with the discrete inputs relating to the base 2, carriage 6 and shuttle 8, and associated controls.
The SRM further includes (see Fig. 3) an analog-to-digital converter 202 having an analog input 204 connected to the analog output 200 of the carriage drive servo 16, and having a digital output 206 connected to the supervisory control means 110. The ~138104 analog output 200 of the carriage drive servo 16 provides a signal indicative of power supplied to the motor and, thus, indicative of the weight of the load 44. The analog-to-digital converter 202 converts the signal from the output 200 of the carriage drive servo 16 to digital format. While other analog-to-digital converters can be employed, in the illustrated embodiment the analog-to-digital converter 202 is a High Resolution Analog card #1771-NBV1.
Every time the shuttle 8 retrieves a load 44(see Fig. 2), the supervisory control means 110 compares the digital value from the analog-to-digital converter 202 to a predetermined value after the load 44 is retrieved and, if the digital value is greater than the predetermined threshold value, the supervisory control means 110 provides an error signal indicating that the load is overweight. The predetermined threshold value is selected based on the handling capacity of the SRM.
The determination of whether or not a newly retrieved load 44 is overweight is preferably made ~1~8104 _ before vertical movement of the carriage 6 is allowed to begin.
Optionally, after the shuttle 8 retrieves a load 44, the supervisory control means 110 disables the carriage drive servo 16 for a predetermined amount of time, e.g. five seconds, stopping movement of the load 44 for the predetermined amount of time before the determination is made as to whether or not the load 44 is overweight. This allows the load 44 and tension member 48 to stabilize before the determination is made as to whether or not the load 44 is overweight.
If the load 44 that has just been picked up by the shuttle 8 is determined to be overweight, an appropriate signal is made to an operator. For example, a message can be sent to an operator screen, a buzzer can be sounded, a light can flash, etc.
Other appropriate action can also be taken. For example, movement of the carriage can be suspended indefinitely until an operator intervenes, or the load can be immediately put back down.
Optionally, but preferably, when the supervisory control means 110 makes a determination that the load H1~19063 44 is not overweight, the supervisory control means 110 additionally makes a determination as to whether or not the load 44 is underweight. This is useful, for example, to determine if the retrieval operation was unsuccessful, or if a box 44 is unexpectedly empty.
In one alternative embodiment of the invention, the combination of the supervisory control means 110 and remote computer 18 can be replaced by a single personal computer. See, for example, U.S. patent application Serial No. 08/042,241, assigned to the assignee of the present invention and incorporated herein by reference.
The base control means 120, carriage control means 130 and shuttle control means 140 each contain a program and the respective parameters of the associated base, carriage and shuttle which the control means 120, 130 and 140 control and which enable movement operation of the base 2, carriage 6 and shuttle 8 at optimum acceleration, deceleration and velocity values. These parameters include the reference positions of the carriage and shuttle, the velocity, acceleration and deceleration rates of the ;~138104 H1~19063 base and carriage, and the deceleration rate of the shuttle.
The distance meter 102 of the base control means 120 transmits an infrared light beam along the aisle path 22 toward the reflector 98 so that a reflected beam is returned to the distance meter 102 to provide a movement indication and distance measurement which locates the position of the base 2 along aisle path 22. Upon receipt of a control instruction on line 112 by the base control means 120 from the supervisory control means 110 requiring a movement of the base 2 along its path to a new position, the control means 120 will compare the new position to which the base is to travel with the base's current position as indicated by the distance meter 102. The means 120 also will concurrently select, on the basis of the direction in which the base is to travel, the acceleration rate, the m~; mllm velocity to which the base can accelerate, and the deceleration rate as the base approaches the new position. Upon selection of these values, the base control means 120 transmits appropriate instruction signals to the base drive means 14, via line 122, for the control of the 2~81~
frequency of the variable frequency power to the base motor 40 to drive the base 2 in the correct direction at the selected m~; ml]m velocity and acceleration and deceleration rates to the new position. The instruction signals include direction, maximum velocity, fast acceleration rate and slow acceleration rate and fast deceleration rate signals for movement in the opposite direction.
During an initialization operation of the SRM, the carriage control means 130 is instructed by the supervisory control means 110 to move the carriage 6 to a home position. Movement of the carriage 6 to the home position will be indicated by the home switch 134 in a response to the control means 130.
The home position of the carriage 6 is a reference position at which the count of the carriage encoder 136 provides a reference indication representing the reference position for all subsequent movements of the carriage and the carriage encoder. Upon receipt of a control instruction on line 114 to the carriage control means 130 from the supervisory control means 110 requiring a pick-up or deposit movement of the carriage 6 along its movement path, the control means ~3~1~4 130 will compare the instructed new position as indicated by the carriage encoder 136. The control means 130 determines the m~iml]m velocity at which the carriage is to travel and selects, upon the basis of the upward or downward direction in which the carriage is to move, the acceleration rate and the deceleration rate upon approaching the new position.
Upon determination of these values, the carriage control means 130 will transmit appropriate instruction signals to the carriage drive servo 16 for the control of the frequency of the variable frequency power to the carriage motor 42 to drive the carriage 6 at the selected acceleration rate, velocity and deceleration rate to move the carriage 6 to the new position.
`~, H1~19063 STORAGE AND RETRIEVAL M~C~TN~
INCLUDING OVERWEIGHT DETECTION
FIELD OF THE INVENTION
The invention relates generally to storage and retrieval machines.
BACKGROUND OF THE INVENTION
Storage and retrieval machines are devices which include a horizontally moveable base, a mast mounted on and extending vertically from the base, a vertically moveable carriage supported by the mast, and a horizontally moveable shuttle, capable of engaging or releasing an object, supported by the carriage. A remote control source gives a comm~n~ to control means on-board the storage and retrieval machine to move the carriage to a particular storage location and either deliver or retrieve an object at the storage location. Either the remote control source or the on-board control means provides specific instructions for movement of the base, the carriage and the shuttle of the storage and retrieval machine. The movement instructions are utilized by further control and/or drive means to operate the ~381 0~
-HE~19063 base, carriage and shuttle to the necessary locations. The movement instructions include, e.g., distance to move or location to move to, maximum velocity, acceleration rate and deceleration rate, for both the base and the carriage.
A typical storage and retrieval machine is capable of handling loads of varying weights.
Examples of storage and retrieval machines are disclosed in U.S. Patent No. 5,170,863 and in U.S.
Patent Application Serial No. 08/042,241, both of which are assigned to the assignee of the present invention and both of which are incorporated herein by reference.
SUMMARY OF THE INVENTION
The invention provides a storage and retrieval machine including a base movable in opposite horizontal directions, a mast mounted on the base, a carriage movable in opposite vertical directions on the mast and capable of carrying a load, and a control system, the control system providing overweight detection for ensuring that the weight of a load picked up by the storage and retrieval machine ~13810~
-H~19063 is not greater than the capacity of the storage and retrieval machine. Motors and motor servos are also provided for moving the base and carriage in their respective opposite horizontal directions or opposite vertical directions. A tension member, such as a rope, belt, chain, etc., is connected to the carriage, is reeved about an upper pulley or sheave, and is engaged by a motor to vertically move the carriage.
One method of ensuring that the weight of the load is not greater than the capacity of the storage and retrieval machine involves using a load cell or strain gauge on the tension member. A problem with this is that it is very expensive.
The inventors of the present invention have recognized that the weight of the load on the carriage puts a tension on the tension member, which tension is directly proportional to the weight of the load. The tension on the tension member results in a load being placed on the motor. The power supplied to the motor to support the load is directly proportional to the weight of the load. The motor servo has an analog current feedback output which ~381b~
'_ H1~19063 provides a signal indicative of power supplied to the motor and which is connected to the control system via an analog-to-digital converter. The analog-to-digital converter converts the signal from the current feedback output of the motor servo to a digital representation. The control system compares this digital representation from the analog-to-digital converter to a predetermined threshold value and, if the digital representation is greater than the predetermined threshold value, the control system provides an error signal indicating that the load is overweight.
In one embodiment of the invention, after the carriage picks up a load, the control system disables the motor servo for a predetermined amount of time, stopping vertical movement of the carriage for a predetermined amount of time before the determination is made as to whether or not the load is overweight.
This allows the load to stabilize before the determination is made as to whether or not the load is overweight.
The invention provides a low cost and simple system for ensuring that the weight of a load picked Z13811~
-up by the storage and retrieval machine is not greater than the capacity of the storage and retrieval machine. Thus, damage to the storage and retrieval machine is avoided.
Other features and advantages of the invention will become apparent to those of ordinary skill in the art upon review of the following detailed description, claims, and drawings.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side elevation view of a storage and retrieval machine incorporating the present invention;
Fig. 2 is a front elevation view of the storage and retrieval machine illustrated in Fig. 1; and Fig. 3 is a schematic circuit diagram for the storage and retrieval machine shown in Figs. 1 and 2 in which the present invention is incorporated.
Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or ~381~4 _ HE~19063 illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
DETAILED DESCRIPTION OF THE
PREFERRED EM~30DIMENT OF THE INVENTION
Shown in Figs. 1-2 of the drawings is a storage and retrieval machine, which is also referred to herein as an SRM. The storage and retrieval machine has a base 2, a mast 4 mounted on and extending upwardly from the base, a carriage 6 movable vertically on a path along the length of the mast 4 to selected vertical locations, a shuttle 8 that is mounted on the carriage 6 for generally horizontal movement and that is capable of picking up and releasing loads, a base and carriage drive means 10 and a control system 12 (Figs. 1 and 3). The base 2 has (see Fig. 1) a length 37 including opposite ends 36 and 38. A drive wheel 28 rotating about an axis 50 and an idler wheel 30 rotating about an axis 56 comprise part of the drive means 10 and are ` ~1381~4 .~
H~19063 respectively mounted on the ends 36 and 38 of the base 2 and roll along a rail 24 supported on a foundation 26 and running through an aisle path 22.
The aisle path 22 extends through a storage area such as a warehouse having stacked storage racks 20.
Upper guide wheels 32 on the mast 4 engage a guide rail 34 to guide the SRM along the rail 24 and maintain the machine in an upright position.
The drive means 10 also includes a base drive 14 controlling a motor 40. The motor 40 is connected to and drives the drive wheel 28 so that the base 2 and thereby the SRM travel in selected opposite directions horizontally and in the direction of the length of the base along the rail 24 to selected locations in the aisle path 22 adjacent to the stacked storage racks 20. At each aisle location of the SRM, the carriage 6 is driven in one of opposite vertical directions to a selected one of the storage racks 20 where the shuttle 8 is driven generally horizontally and in directions transverse to the aisle path 22 into a storage rack to deliver or retrieve a load object such as box 44 carried on the shuttle as shown in Figs. 1 and 2.
21381û4 The drive means 10 further includes (see Fig. 3) a carriage drive servo 16, having an analog output 200. The drive means 10 further includes (see Figs.
1 and 3) a carriage motor 42. The carriage motor 42 is controlled by the carriage drive servo 16 and is connected to and acts through a drum assembly 82 (Fig. 1) to drive the carriage 6. While other motor servos could be employed, in the illustrated embodiment of the invention, the carriage drive servo 16 is an Indramat servo amplifier #KDS 1.1-150-300 W1/220, and has an analog output 200 providing 50mV
per Amp, with a range of zero to five Volts DC. The motor 42 and the drum assembly 82 are both mounted on a frame 46 (Fig. 1) which comprises part of the base 2. The motor 42 drives the drum assembly 82, and thereby extends or retracts a tension member 48 which is part of the assembly 82, and which is reeved over a sheave or pulley 52 on the mast 4 and is connected to the carriage 6. The tension member 48 can be a rope, a chain, a belt, or any other suitable flexible member. A cabinet 54 is also mounted on the base 2 for enclosing a portion of the components of the control system 12. Suitable means (not shown) is 810~
~.
~ 19063 provided for supplying electrical power for the various drives and the control system 12 of the SRM
described hereinafter.
The carriage 6 includes (see Fig. 2) a frame 60 upon which the shuttle 8 is mounted and to which is connected the tension member 48 for moving the carriage 6 vertically along the mast 4 in response to the operation of the carriage motor 42 and the drum assembly 82. The carriage 6 is movably supported and guided on the mast 4 by means of upper support rollers 62, 64 and 66, 68 rotatably mounted on an upper section 70 of the frame 60, and by means of lower support rollers 72, 74, and 76, 78 rotatably mounted on a lower section 80 of the frame 60.
The shuttle 8 comprises a shuttle drive means 90 (Fig. 1) mounted on the lower section 80 of the carriage frame 60, a lower base plate 92 (Fig. 2) also mounted on the lower frame section 80, an intermediate plate 94 (Fig. 1), a top plate 96, and a shuttle telescoping drive 100. Operation of the shuttle telescoping drive 100 by the shuttle drive means 90 causes the plates 94 and 96 to extend in a telescoping fashion to the position shown in Fig. 2 ~138104 -H1~19063 and retract to a centered position on the lower frame section 80. The shuttle 8 thus operates in conjunction with the base 2 and carriage 6 to deposit the load 44 in or retract the load 44 from a storage rack 20.
The control system 12 is illustrated in greater detail in Fig. 3 and includes: a supervisory control means 110 which receives operating comm~n~
information on lines 88 from a remote computer 18; a base control means 120 for controlling the movement of the base 2 of the SRM along a path of travel in the aisle path 22; a carriage control means 130 for controlling the movement of the carriage 6 along a path of travel on the mast 4; and a shuttle control means 140 for controlling the extending and retracting movement of the shuttle 8 into and out of a storage rack 20. The supervisory control means 110 has connections to the base control means 120, the carriage control means 130 and the shuttle control means 140 respectively represented by lines 112, 114 and 116.
The SRM includes (see Fig. 3) a distance meter 102 connected by a line 104 to the base control means ~3~1~4 ~19063 120, a reflector 98 located at the end of the aisle path 22, and a proximity photocell 106 connected to the supervisory control means 110 by a line 108. The SRM also includes a carriage encoder 136 connected to the control means 130 by a line 138, and a home switch 134 connected to the carriage control means 130 by a line 118. Other means of determ-n'ng and controlling the position of the base 2, shuttle 8, and carriage 6 may be employed.
The supervisory control means 110 may comprise, for example, a programmable logic controller (PLC) which is programmed to produce specific operating instructions to the base control means 120, the carriage control means 130 and the shuttle control means 140 in response to the operating comm~n~ from the remote computer 18. While other PLCs may be employed, in the illustrated embodiment the PLC is an Allen-Bradley PLC 5/20 #1785-120B. The operating information from the remote computer 18 is normally a comm~n~ to pick up or deposit a load object 44 or to move to a specified location. The information from the remote computer 18 is converted to RS232C format form and is then converted to a memory block of ASCII
~138104 -H1~19063 characters in binary code form at an input module of the supervisory control means 110. The supervisory control means 110 also has various discrete inputs for receiving operating condition indications relating to the base 2, carriage 6 and shuttle 8 and their associated controls. These include an input on the line 108 from the proximity photocell 106 indicating the location of the base 2 along the aisle path 22, an input on line 118 from the home switch 134 indicating if the carriage 6 is at its reference home position, and inputs (not shown) indicating the position of and the full or empty condition of the shuttle. The supervisory control means 110 produces control instructions in response to not only the operating comm~n~ received from the remote computer 18, but also in accord with the discrete inputs relating to the base 2, carriage 6 and shuttle 8, and associated controls.
The SRM further includes (see Fig. 3) an analog-to-digital converter 202 having an analog input 204 connected to the analog output 200 of the carriage drive servo 16, and having a digital output 206 connected to the supervisory control means 110. The ~138104 analog output 200 of the carriage drive servo 16 provides a signal indicative of power supplied to the motor and, thus, indicative of the weight of the load 44. The analog-to-digital converter 202 converts the signal from the output 200 of the carriage drive servo 16 to digital format. While other analog-to-digital converters can be employed, in the illustrated embodiment the analog-to-digital converter 202 is a High Resolution Analog card #1771-NBV1.
Every time the shuttle 8 retrieves a load 44(see Fig. 2), the supervisory control means 110 compares the digital value from the analog-to-digital converter 202 to a predetermined value after the load 44 is retrieved and, if the digital value is greater than the predetermined threshold value, the supervisory control means 110 provides an error signal indicating that the load is overweight. The predetermined threshold value is selected based on the handling capacity of the SRM.
The determination of whether or not a newly retrieved load 44 is overweight is preferably made ~1~8104 _ before vertical movement of the carriage 6 is allowed to begin.
Optionally, after the shuttle 8 retrieves a load 44, the supervisory control means 110 disables the carriage drive servo 16 for a predetermined amount of time, e.g. five seconds, stopping movement of the load 44 for the predetermined amount of time before the determination is made as to whether or not the load 44 is overweight. This allows the load 44 and tension member 48 to stabilize before the determination is made as to whether or not the load 44 is overweight.
If the load 44 that has just been picked up by the shuttle 8 is determined to be overweight, an appropriate signal is made to an operator. For example, a message can be sent to an operator screen, a buzzer can be sounded, a light can flash, etc.
Other appropriate action can also be taken. For example, movement of the carriage can be suspended indefinitely until an operator intervenes, or the load can be immediately put back down.
Optionally, but preferably, when the supervisory control means 110 makes a determination that the load H1~19063 44 is not overweight, the supervisory control means 110 additionally makes a determination as to whether or not the load 44 is underweight. This is useful, for example, to determine if the retrieval operation was unsuccessful, or if a box 44 is unexpectedly empty.
In one alternative embodiment of the invention, the combination of the supervisory control means 110 and remote computer 18 can be replaced by a single personal computer. See, for example, U.S. patent application Serial No. 08/042,241, assigned to the assignee of the present invention and incorporated herein by reference.
The base control means 120, carriage control means 130 and shuttle control means 140 each contain a program and the respective parameters of the associated base, carriage and shuttle which the control means 120, 130 and 140 control and which enable movement operation of the base 2, carriage 6 and shuttle 8 at optimum acceleration, deceleration and velocity values. These parameters include the reference positions of the carriage and shuttle, the velocity, acceleration and deceleration rates of the ;~138104 H1~19063 base and carriage, and the deceleration rate of the shuttle.
The distance meter 102 of the base control means 120 transmits an infrared light beam along the aisle path 22 toward the reflector 98 so that a reflected beam is returned to the distance meter 102 to provide a movement indication and distance measurement which locates the position of the base 2 along aisle path 22. Upon receipt of a control instruction on line 112 by the base control means 120 from the supervisory control means 110 requiring a movement of the base 2 along its path to a new position, the control means 120 will compare the new position to which the base is to travel with the base's current position as indicated by the distance meter 102. The means 120 also will concurrently select, on the basis of the direction in which the base is to travel, the acceleration rate, the m~; mllm velocity to which the base can accelerate, and the deceleration rate as the base approaches the new position. Upon selection of these values, the base control means 120 transmits appropriate instruction signals to the base drive means 14, via line 122, for the control of the 2~81~
frequency of the variable frequency power to the base motor 40 to drive the base 2 in the correct direction at the selected m~; ml]m velocity and acceleration and deceleration rates to the new position. The instruction signals include direction, maximum velocity, fast acceleration rate and slow acceleration rate and fast deceleration rate signals for movement in the opposite direction.
During an initialization operation of the SRM, the carriage control means 130 is instructed by the supervisory control means 110 to move the carriage 6 to a home position. Movement of the carriage 6 to the home position will be indicated by the home switch 134 in a response to the control means 130.
The home position of the carriage 6 is a reference position at which the count of the carriage encoder 136 provides a reference indication representing the reference position for all subsequent movements of the carriage and the carriage encoder. Upon receipt of a control instruction on line 114 to the carriage control means 130 from the supervisory control means 110 requiring a pick-up or deposit movement of the carriage 6 along its movement path, the control means ~3~1~4 130 will compare the instructed new position as indicated by the carriage encoder 136. The control means 130 determines the m~iml]m velocity at which the carriage is to travel and selects, upon the basis of the upward or downward direction in which the carriage is to move, the acceleration rate and the deceleration rate upon approaching the new position.
Upon determination of these values, the carriage control means 130 will transmit appropriate instruction signals to the carriage drive servo 16 for the control of the frequency of the variable frequency power to the carriage motor 42 to drive the carriage 6 at the selected acceleration rate, velocity and deceleration rate to move the carriage 6 to the new position.
Claims (20)
1. A storage and retrieval machine comprising:
a base movable along a horizontal path;
a mast mounted on said base;
a carriage movable on said mast along a vertical path and including a load supporting surface;
a motor for moving said carriage along said mast;
a drive for controlling said motor to cause said motor to selectively move said carriage in either direction along the vertical path, said drive providing an output signal representative of load on said motor;
a comparator for comparing said output signal to a predetermined value; and an indicator for indicating that the load on said carriage is too heavy if said output signal is greater than the predetermined value.
a base movable along a horizontal path;
a mast mounted on said base;
a carriage movable on said mast along a vertical path and including a load supporting surface;
a motor for moving said carriage along said mast;
a drive for controlling said motor to cause said motor to selectively move said carriage in either direction along the vertical path, said drive providing an output signal representative of load on said motor;
a comparator for comparing said output signal to a predetermined value; and an indicator for indicating that the load on said carriage is too heavy if said output signal is greater than the predetermined value.
2. A storage and retrieval system in accordance with claim 1 wherein said comparator does not compare said output signal to said predetermined value until a predetermined time period has elapsed after a load is placed on said carriage.
3. A storage and retrieval system in accordance with claim 1 wherein said motor does not operate to move said carriage during said predetermined time period.
4. A storage and retrieval system in accordance with claim 1 wherein said drive comprises a motor servo drive.
5. A storage and retrieval system in accordance with claim 4 and further comprising a PLC
electrically connected to said servo drive and controlling said servo drive, said PLC including said comparator.
electrically connected to said servo drive and controlling said servo drive, said PLC including said comparator.
6. A storage and retrieval system in accordance with claim 5 wherein said servo drive has an analog output, and wherein said output signal representative of load on said motor is the analog output of said servo drive.
7. A storage and retrieval system in accordance with claim 6 wherein said drive also comprises an analog-to-digital converter connected between said analog output of said servo drive and said PLC.
8. A storage and retrieval system in accordance with claim 1 wherein said carriage includes means for picking up and depositing a load.
9. A storage and retrieval system in accordance with claim 1 and further comprising an encoder which is connected to said digital control system and which provides pulses in response to movement of said carriage, and wherein said digital control system determines where said carriage is located along said mast using said encoder.
10. A storage and retrieval machine comprising:
a generally vertically extending mast;
a carriage movable along said mast and including a load supporting surface;
an electric motor which moves said carriage along said mast;
a digital control system capable of performing logic;
an analog-to-digital converter; and a servo, receiving instructions from said digital control system, and supplying power to said motor based on said instructions to selectively cause said motor to move said carriage, said servo having an analog current feedback output which provides a signal indicative of power supplied to the motor and which is connected to the control system via said analog-to-digital converter, wherein said digital control system compares the digitized value of power supplied to said motor to a predetermined value and wherein, if the digitized value of power supplied to the motor is greater than a predetermined threshold, said control system provides an error signal indicating that the load is overweight.
a generally vertically extending mast;
a carriage movable along said mast and including a load supporting surface;
an electric motor which moves said carriage along said mast;
a digital control system capable of performing logic;
an analog-to-digital converter; and a servo, receiving instructions from said digital control system, and supplying power to said motor based on said instructions to selectively cause said motor to move said carriage, said servo having an analog current feedback output which provides a signal indicative of power supplied to the motor and which is connected to the control system via said analog-to-digital converter, wherein said digital control system compares the digitized value of power supplied to said motor to a predetermined value and wherein, if the digitized value of power supplied to the motor is greater than a predetermined threshold, said control system provides an error signal indicating that the load is overweight.
11. A storage and retrieval system in accordance with claim 10 wherein said digital control system does not compare said output signal to said predetermined value until a predetermined time period has elapsed after a load is placed on said carriage.
12. A storage and retrieval system in accordance with claim 11 wherein said motor does not operate to move said carriage during said predetermined time period.
13. A storage and retrieval system in accordance with claim 10 wherein said digital control system comprises a PLC.
14. A storage and retrieval system in accordance with claim 13 wherein, after a load is placed on said carriage, said PLC disables said servo to prevent movement of said carriage in the vertical direction, for a predetermined period of time, before said digital control system compares said output signal to said predetermined value.
15. A storage and retrieval system in accordance with claim 10 wherein said digital control system comprises a computer.
16. A storage and retrieval system in accordance with claim 15 wherein said digital control system comprises a personal computer.
17. A storage and retrieval system in accordance with claim 10 wherein said carriage includes means for picking up and depositing a load.
18. A storage and retrieval system in accordance with claim 13 wherein said carriage includes means for picking up and releasing a load, and wherein, after a load is placed on said carriage, said PLC disables said servo to prevent movement of said carriage in the vertical direction, for a predetermined period of time, before said digital control system compares said output signal to said predetermined value.
19. A storage and retrieval system in accordance with claim 10 and further comprising an encoder which is connected to said digital control system and which provides pulses in response to movement of said carriage, and wherein said digital control system determines where said carriage is located along said mast using said encoder.
20. A storage and retrieval machine comprising:
a generally vertically extending mast having a top and a bottom;
a pulley supported proximate the top of said mast;
a carriage movable along said mast and including a load supporting surface;
a drum assembly;
an electric motor drivingly connected to said drum assembly to rotate said drum assembly;
a tension member wound around said drum assembly and capable of being extended from and retracted by said drum assembly in response to rotation of said drum assembly, said tension member being reeved about said pulley and connected to said carriage;
a digital control system capable of performing logic;
an analog-to-digital converter; and a servo, receiving instructions from said digital control system, and supplying power to said motor based on said instructions to selectively cause said motor to rotate said drum assembly and move said carriage, said servo having an analog current feedback output which provides a signal indicative of power supplied to the motor and which is connected to the control system via said analog-to-digital converter, wherein said digital control system compares the digitized value of power supplied to said motor to a predetermined value and wherein, if the digitized value of power supplied to the motor is greater than a predetermined threshold, said control system provides an error signal indicating that the load is overweight.
a generally vertically extending mast having a top and a bottom;
a pulley supported proximate the top of said mast;
a carriage movable along said mast and including a load supporting surface;
a drum assembly;
an electric motor drivingly connected to said drum assembly to rotate said drum assembly;
a tension member wound around said drum assembly and capable of being extended from and retracted by said drum assembly in response to rotation of said drum assembly, said tension member being reeved about said pulley and connected to said carriage;
a digital control system capable of performing logic;
an analog-to-digital converter; and a servo, receiving instructions from said digital control system, and supplying power to said motor based on said instructions to selectively cause said motor to rotate said drum assembly and move said carriage, said servo having an analog current feedback output which provides a signal indicative of power supplied to the motor and which is connected to the control system via said analog-to-digital converter, wherein said digital control system compares the digitized value of power supplied to said motor to a predetermined value and wherein, if the digitized value of power supplied to the motor is greater than a predetermined threshold, said control system provides an error signal indicating that the load is overweight.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US32652894A | 1994-10-20 | 1994-10-20 | |
| US326,528 | 1994-10-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2138104A1 true CA2138104A1 (en) | 1996-04-21 |
Family
ID=23272603
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2138104 Abandoned CA2138104A1 (en) | 1994-10-20 | 1994-12-14 | Storage and retrieval machine including overweight detection |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2138104A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106970642A (en) * | 2017-04-20 | 2017-07-21 | 佛山科学技术学院 | A kind of multi-rotor unmanned aerial vehicle state monitoring apparatus |
-
1994
- 1994-12-14 CA CA 2138104 patent/CA2138104A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106970642A (en) * | 2017-04-20 | 2017-07-21 | 佛山科学技术学院 | A kind of multi-rotor unmanned aerial vehicle state monitoring apparatus |
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