EE324 Lab 6 Elevator Controller Page 1/6

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1 EE324 Lab 6 Elevator Controller Page 1/6 Overview This lab involves the creation of a controller for a two-floor elevator simulator. A circuit that uses Digilab s seven-segment displays to simulate elevator behavior will be provided (see figure below). You must design and implement an elevator controller that uses the simulator circuit to create an elevator with typical features. Background The elevator simulator requires 10 external inputs (see table below). Two of these inputs model user inputs (push buttons), and eight model sensor inputs. By asserting sensor inputs at times when they would normally be expected, normal elevator operation can be simulated. By failing to assert the sensor inputs, broken sensors can be simulated, and error conditions can be simulated as well. Simulates elevator car moving up and down Simulates inner door at upper level Simulates outer door at upper level Simulates walls Simulates door at lower level Simulates inner door at lower level Lower level doors closed Lower level doors open Elevator in motion Upper level doors open Seven-segment display elevator simulator Four examples of elevator simulator states The table on the right defines the inputs required for a simple elevator. The button inputs arise from the exterior call buttons on either floor, and from the interior go buttons inside the cabin. Note, however, that the AU and GU signals perform similar functions; if either is pressed, the elevator goes up. Similarly, pressing either the GL or AL buttons will cause the elevator to go down. This observation can be exploited to remove two signals from the controller; button up (BU) can be formed from (AU or GU), and button down (BD) can be formed from (AL or GL). Note that the following block diagram uses the BU and BL signals. Elevator Controller Inputs Source Description Signal Interior buttons Go upper level GU Go lower level GL Exterior buttons Call upper level AU Call lower level AL Door sensors External upper door open UO External lower door open LO Internal door open IO External upper door closed UC External lower door closed LC Internal door closed IC Location sensors At upper level LU At lower level LD Timer Timer expired T

2 EE324 Lab 6 Elevator Controller Page 2/6 The controller does not need to latch the input signals, so that the BU and BL inputs are considered only when then elevator is waiting at the top or bottom floor with closed doors. The eight sensor inputs would normally arise from physical sensors within the elevator system the elevator simulator assumes these sensors are present and functional. To provide more realistic test cases, eight inputs have been added to deactivate each sensor so that failure conditions can be simulated. The timerexpired input(t) arises from an internal counter that serves as an interval timer. The controller must produce the output signals shown below. The outputs should be produced in accordance with the following general requirements of elevator operation. A block diagram for the elevator controller is shown on the right below. Elevator Controller Outputs Function Description Signal Main motor drive Main motor up MU Main motor down MD Door actuators Close upper outer doors CU Close lower outer doors CL Close inner door Open upper outer door OU Open lower outer door OL Open inner door Timer Timer enable TE General Requirements The following discussion does not precisely specify all requirements; rather, only the general requirements are presented. It is assumed that good engineering judgment and a general knowledge of elevator function can be applied to fill in the blanks to arrive at a final design specification. T UO UC LO LC IO IC LU LD BU BL CLK RST CL CU ET MD MU OL OU Elevator Controller Block Diagram The elevator must respond to a call request at the upper or lower floor by: proceeding to the floor if not already there; opening the doors for a sufficient amount of time; closing the doors, and then waiting for an internal button press. A timer module is provided that to generate sufficient wait times (accessed via the Timer and Timer enable signals). The timer function should be enabled only when it is required, and left inactive at all other times. When an internal button is pressed, the elevator should proceed to the requested floor. It the elevator is already at the requested floor, both doors (internal and external) should simply open. If both the BU and BL inputs are asserted simultaneously while the elevator is not in motion, then assume the elevator is already at the requested floor. Note that the elevator simulator will show some error conditions if you make an improper design assumption (hint: if the elevator car flashes, keep thinking!). Lab procedure Obtain a copy of the elevator simulator from the lab7 subdirectory at the class distribution site (which is \\cse\home$ under the ee324 directory, with filename elev_asg). The best way to obtain a copy is to

3 EE324 Lab 6 Elevator Controller Page 3/6 open the simulator project from within the Xilinx project manager, and then choose file copy project, with your own directory as the destination. Prepare an accurate and complete state diagram for the elevator controller. Then design and implement a state machine for the controller using the Xilinx VHDL tool. Your VHDL code must contain one single process statement that does nothing but implement the state register; no other restrictions will be placed on your coding style. (The Xilinx state editor does not produce code that uses this state register process style, which effectively means that you must write your own VHDL code.) Fully test your design both in the simulator and in the Xilinx FPGA. When you are satisfied that it works correctly, print copies of your VHDL source code, top-level schematic, and simulation outputs. Include these documents in a brief lab write-up (no more that one page!) together with your state diagram. Input pins locations have been assigned as shown in the table on the right. Outputs are pre-assigned to drive the seven-segment LED display. The global asynchronous reset should drive the state machine to the state of waiting at the upper level with closed doors. The global asynchronous reset is also connected to the provided elevator simulator circuit. Sensors Signal Function Pin DLU Disable sensor 0 for broken sensor SW8 DLD Disable sensor 0 for broken sensor SW7 DUC Disable sensor 0 for broken sensor SW6 DUO Disable sensor 0 for broken sensor SW5 DIC Disable sensor 0 for broken sensor SW4 DIO Disable sensor 0 for broken sensor SW3 DLC Disable sensor 0 for broken sensor SW2 DLO Disable sensor 0 for broken sensor SW1 Buttons BU Button Up BTN4 BL Button Down BTN3 Reset System reset (asynchronous) BTN1 The write-up for this lab should include a paragraph explaining the design requirements and design intent, and a second paragraph explaining the work that was completed. Note that the first paragraph can refer to this document a controller consistent with the requirements of the lab7 document was designed. Somewhere in these first two paragraphs, you should include information about the tool sets that were used, the status of the design at the time the document is written, and any special circumstances or design features (the door open sensor does not work because ). In a third and final paragraph, provide a brief technical explanation of the circuit that you designed. Use references to your state diagram and comments in your VHDL code to describe the circuit, instead of wordy explanations. Normally, in a technical description like this, a table that defined all inputs and outputs to and from the controller would be included. Since these tables were provided to you, you can simply refer to them. But you should include particular information about the input and output signals that were not included in the provided tables (e.g., any input debouncing or output filtering operations). Finally, include a space for the TA to sign to indicate that the design was successfully demonstrated. It will be assumed that reports submitted without such a signature reflect designs that were not completed.

4 EE324 Lab 6 Elevator Controller Page 4/6 Discussion This state machine design is larger than most that you have attempted so far. It s important to attack the design in a methodical way, building understanding of the design as you proceed. Remember that sketching numerous iterations of a state machine is typical, and that the act of sketching a state machine is design. When designing your state machine, you must (as always) first decide which behaviors require a state, and which do not. For example, you will probably want to consider assigning states to activities such as calling from upper level, calling from lower level, opening doors at upper level, opening doors at lower level, waiting at upper level with doors open, etc. You will probably not assign states to such activities as pressing button upper level (this is a user activity, not a machine state), stop main motor (this is an output from a state, not a state in its own right), or doors closed lower level (this is an input to a state). Use your knowledge of elevator function together with the available inputs and outputs to define a complete list of states. When you have decided on a list of states, place all the states in a diagram and begin to add control flow (inputs) and outputs from various states. Continually check your design against requirements, and be sure that all inputs and all outputs are accounted for. Good luck!

5 EE324 Lab 7 Elevator controller Page 5/6 State machine and I/O descriptions Inputs: Buttons: - inner - Go Upper level = GU - Go Lower level = GL - outer - Appeal Upper level = AU - Appeal Lower level = AL Sensors: - doors - external Upper door Open = UO - external Lower door Open = LO - Inner door Open = IO - external Upper door Closed = UC - external Lower door Closed = LC - Inner door Closed = IC - level arrived - Level Up arrived = LU - Level Down arrived = LD - timer - Timer out = T States: Waiting at Upper level Closed doors Elevator Going Down Opening Doors at Lower level Waiting at Lower level Open doors Closing Doors at Lower level Waiting at Lower level Closed doors Elevator Going Up Opening Doors at Upper level Waiting at Upper level Open doors Closing Doors at Upper level = WUC = EGD = ODL = WLO = CDL = WLC = EGU = ODU = WUO = CDU Outputs: Main motor: - Go Up = MU - Go Down = MD Doors: - Close Upper door = CU - Close Lower door = CL - Close Inner door = - Open Upper door = OU - Open Lower door = OL - Open Inner door = Timer: - Enable Timer = ET (timer is reset all the time when ET=0) Hint: because inputs GU and AU will appear every time as (GU + AU) = BU or (GU + AU) = GU AU = BU, functions BU and BU will be used instead of (GU + AU) and (GU + AU) = GU AU. Similarly, inputs GL and AL will be replaced by functions: BL = ( GL + AL ) and BL = ( GL + AL ) = GL AL

6 EE324 Lab 7 Elevator controller Page 6/6 The (incomplete) State Diagram WUC EGD MD CU CDU ODL OL ET WUO WLO ET OU ODU CDL CL MU EGU WLC