# US 7,743,890 B2 · Method and system for determining instantaneous peak power consumption in elevator banks

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- Number: US 7,743,890 B2
- Document ID: US7743890B2
- Status: Granted
- Kind: B2
- Application number: 11/761,683
- Filed: 2007-06-12
- Published: 2008-12-18
- Granted: 2010-06-29
- Earliest claimed: 2007-06-12
- Assignees: Mitsubishi Electric Research Laboratories, Inc.
- Inventors: Daniel N. Nikovski; Matthew E. Brand
- Web page: https://patentgrep.com/patent/US7743890B2

## CPC

- B66B 1/2458: {For elevator systems with multiple shafts and a single car per shaft}
- B66B 2201/102: Up or down call input
- B66B 2201/211: Waiting time, i.e. response time
- B66B 2201/212: Travel time
- B66B 2201/216: Energy consumption
- B66B 2201/222: Taking into account the number of passengers present in the elevator car to be allocated
- Y02B 50/00: Energy efficient technologies in elevators, escalators and moving walkways, e.g. energy saving or recuperation technologies
- B66B: ELEVATORS; ESCALATORS OR MOVING WALKWAYS ({apparatus for raising or lowering persons on theatrical stages or the like A63J5/12} ; funicular railbound systems with rigid ground-supported tracks and cable traction, e.g. cliff railways, B61B9/00; arrangements of ammunition handlers in vessels B63G3/00; hoists, lifts, or conveyors for loading or unloading in general B65G; braking or detent devices controlling normal movements of winding drums or barrels B66D; ship-lifting devices E02C; garages for many vehicles with mechanical means for lifting vehicles E04H6/12; hoists for feeding ammunition or projectiles to launching apparatus or to loading mechanisms F41A9/00)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A method and system determine peak power consumption over time by a bank of elevator for servicing a set of passenger hall calls and delivery requests, and selecting elevator schedules that keep peak power consumption below a predetermined threshold. For each car in response to receiving a hall call, a set of all possible paths to service all hall calls assigned to the car are determined, in which each path includes a set of all possible segments. A peak power consumption for each possible segment is also determined. The peak power consumptions for the set of all possible segments for each time instant are added to determine a total peak power consumption for each time instant, and a particular path is selected as a schedule to operate the bank of elevator cars, if the total peak power consumption for any instant in time while operating according to the selected schedule is below a predetermined threshold.

## Claims

### Claim 1

A method for determining, for any instant in time, total peak power consumption for a bank of elevator cars, comprising;
determining, for each car in response to receiving a hall call, a set of all possible paths to service all hall calls assigned to the ear, in which each path includes a set of all possible segments;
determining a peak power consumption for each possible segment;
adding the peak power consumptions for the set of all possible segments for each time instant to determine a total peak power consumption for each time instant; and
selecting a particular path as a schedule to operate the bank of elevator cars, if the total peak power consumption for any instant in time while operating according to the selected schedule is below a predetermined threshold.

### Claim 2 (depends on 1)

The method of claim 1 wherein the set of all possible paths of each car depend on a current state of the elevator system, and further comprising:
defining the current state of the elevator system by passengers having assigned cars, and for each car a direction of travel, a position, and a velocity of the car.

### Claim 3 (depends on 1)

The method of claim 1 further comprises:
organizing the set: of all possible states in a corresponding dynamic programming trellis, and wherein transitions between the states correspond to the set of all possible path segments.

### Claim 4 (depends on 1)

The method of claim 1 further comprising:
associating each segment with a power profile.

### Claim 5 (depends on 1)

The method of claim 1, in which the bank of elevator cars includes traction sheave elevators without counterweights.

### Claim 6 (depends on 1)

The method of claim 1, in which a destination associated with the hall call is unknown.

### Claim 7 (depends on 1)

The method of claim 1, in which the peak power consumed when following a particular path p is ƒp(t), and the total peak power is F(t)=maxpεPƒp(t), where P is the set of all possible paths.

### Claim 8 (depends on 1)

The method of claim 1, further comprising:
modeling the set of all possible segments with a phase-space diagram.

### Claim 9 (depends on 8)

The method of claim 8, in which the total peak power consumption. F(t) at a particular instant in time t is a nested maximization.
F(t)=maxsεSmaxτεγsƒs(t, τ), where S is a set of all possible segments of the phase-space diagram, and γs is the set of all possible starting times τ for realizations of a particular segment s.

### Claim 10 (depends on 9)

The method of claim 9, in which the realization of the particular segment s depends on the starting time τ of the realization, and a profile of the total peak power consumption is time-invariant
ƒs(t, τ)=ƒs(t+Δt, τ+Δτ),
for any time interval Δt,

### Claim 11 (depends on 10)

The method of claim 10, in which the peak power profile Fs(t) of the segment s is approximated by a first part: for tε[tmin, t*), Fs(t)=ƒs(t, tmin), a second part: for tε[tmin+t*, tmax+t*]), Fs(t)=ƒs(tmin+t*, tmin)=ƒs(t*, 0), and a third part: for tε(tmax+t*, tmax+t1]), Fs(t)=ƒs(t, tmax), where t* is a time of peak power consumption, and tmin is an earliest time and tmax is a latest time when traversal of segment s can start, respectively.

### Claim 12 (depends on 11)

The method of claim 11, in which the earliest time tmin and the latest time tmax when a traversal of segment s can start are determined by means of dynamic programming, using recurrent equalities
tqmin=minrεR[trmin+Δt(r, q)], and
tqmax=maxrεR[trmax+Δt(r, q)], and
where q is the state of the trellis at the beginning of segment s, and R is the set of states at the beginning of segments which end with state q, and Δt(r, q) is a duration of the segment between state r and state q.

### Claim 13 (depends on 12)

The method of claim 12, in which the determination of the earliest and the latest start times for each segment is performed in a single pass over the state of the trellis, starting from an upper right end of the trellis and proceeding row-by-row towards a bottom row of the trellis, while proceeding right to left within each consecutive row.

### Claim 14 (depends on 13)

The method of claim 13, in which the earliest: time tmin and the latest time tmax, as well as maximization of the peak power for any moment in time between the earliest time tmin and the latest time tmax is updated during the same pass over the trellis, such that F(t) is assigned a value of Fs(t), if the previous estimate of F(t) is lower than Fs(t).

### Claim 15 (depends on 14)

The method of claim 14, in which the update is performed for a discrete set of time moments t(i)=iΔt, i=0, I, for a selected time step Δt, such that F(i)=F(t(i))=F(iΔt), and F(i) is assigned a value of Fs(iΔt)s if a previous estimate of F(i) is lower than Fs(iΔt).

### Claim 16 (depends on 15)

The method of claim 15, where all peak power profiles F(i) for each car are added up separately for each time instance t(i), and the schedule is accepted only if the sums of the total peak power for all time instances t(i) is below a predetermined threshold,

### Claim 17 (depends on 1)

The method of claim 1, in which the bank of elevator cars includes traction sheave cars with counterweights.

### Claim 18

A system determines, for any instant in time, total peak power consumption for a bank, of elevator cars, comprising:
means for determining, for each car in response to receiving a hall, call, a set of all possible paths to service all hall calls assigned to the car, in which each path includes a set of all possible segments;
means for determining a peak power consumption for each possible segment;
means for adding the peak power consumptions for the set of all possible segments for each time instant to determine a total peak power consumption for each time instant; and
means for selecting a particular path as a schedule to operate the bank of elevator cars, if the total peak power consumption for any instant in time while operating according to the selected schedule is below a predetermined threshold.

### Claim 19 (depends on 18)

The system of claim 18 wherein, the set of all possible paths of each car depend on a current state of the elevator system, and further comprising:
means for defining the current state of the elevator system by passengers having assigned cars, and for each car a direction of travel, a position, and a velocity of the car.