EP0733580A2 - Running gear having damped pendulum oscillations - Google Patents

Abstract

The output shaft (2) of an induction motor (1) is coupled mechanically to a free-wheel device (3) on the input shaft (4) of the reduction gear (5) driving the wheels (7) on running rails (8). The system has a free-wheel characteristic in the sense that when an externally applied force tends to accelerate the travel of the crane, there is a cessation of power transmission from the drive train to the wheels. During the half-period of oscillation when the load swings ahead of the crane, there is no forced constraint on the latter.

Description

In practice, it is known to equip trolleys of hoists with asynchronous motors when it comes to the fact that the hoists can run along a rail in a power-driven manner. Asynchronous motors run at essentially constant speeds and, as a rule, they also have a relatively strong starting torque, which leads to jerky acceleration when the undercarriage starts. This strong acceleration is not disturbing as long as the chain of the hoist is not significantly extended, i.e. the load is not significantly reduced. It becomes problematic when starting with a load that is lowered over a long chain.

The chassis equipped with an asynchronous motor accelerates quickly and changes to a constant driving speed after a short driving distance. The consequence of the jerky acceleration of the undercarriage is that the load hanging on the extended chain begins to oscillate and the oscillation does not stop even when the undercarriage is moving at a constant speed moved on. The movement of the load can be broken down into two components, namely a uniform movement in the direction of travel and an oscillating movement which tends to alternately decelerate or accelerate the undercarriage. Because of the hard characteristic of the asynchronous motor, the undercarriage cannot follow this force induced by the pendulum motion, which is why the undercarriage acts like a rigid, fixed suspension for the pendulum motion component.

For this reason, a number of proposals have already been made in practice to regulate the speed of the asynchronous motor so that the oscillation is either avoided as far as possible or damped as much as possible. The metrological effort that is necessary for this and also the control devices are very complex.

Proceeding from this, it is an object of the invention to provide a trolley for hoists which, with less effort, causes the load hanging on the support member to oscillate less or quickly dampens the load oscillation.

This object is achieved by a chassis with the features of claim 1.

In a drive system with free-wheeling characteristics, the undercarriage can follow the pendulum movement because when the load swings forward, the undercarriage can follow the load. These properties of the drive system make it possible to convert the pendulum energy into driving energy, which means that after a relatively short distance, the load oscillation has come to a standstill and the load is moving at the same speed as the chassis.

However, the processes that lead to rapid damping of the load oscillation in the new solution have not yet been fully clarified. The following context of action is suspected:

If the undercarriage is accelerated by the motor when the hook load is at rest, the undercarriage has already moved a considerable distance from the rest position before the load hanging on the hook is accelerated in the direction of travel. If a jerky acceleration occurs from standstill, a load oscillation is induced by the jerky acceleration. As a result of the load oscillation, the load will endeavor to run ahead of the chassis after a certain travel distance of the chassis, i.e. the swinging load in turn pulls the undercarriage and tries to accelerate it. In contrast to simple asynchronous motors, the chassis equipped with the new drive system can follow this acceleration caused by the load swinging. In this way, the energy contained in the oscillating load is converted into driving energy that keeps the running gear moving. Only when the running speed of the undercarriage drops below the setpoint again will the drive system again provide propulsion for the undercarriage, although a substantial part of the pendulum energy has already been converted into drive energy. In this way, the load oscillation is already largely dampened when the load is overhauled for the first time.

Such a drive characteristic can be achieved either by means of an asynchronous motor with freewheeling or with the aid of a motor with a main closing characteristic. This is because the motor with the main fault characteristic cannot act as a brake, because there is no speed at which a generator effect can occur as long as the polarity between the armature and the field winding is not changed.

In addition, the universal motor working in the main circuit has a very soft speed-torque characteristic.

In addition, this is supported by the fact that the electronic control regulating the universal motor at constant speed throttles or switches off the power supply for the universal motor if the universal motor is brought to speeds which are above the desired speed as a result of the load oscillation.

Apart from these effects, the load oscillation is reduced in any case in a chassis with a regulated universal motor as the drive, because this type of drive reduces jerky accelerations.

The flexibility of the travel drive can be further increased if the switch arrangement has at least a third switching state in which the power supply to the motor is possible. Either a further rigid driving speed or the "accelerate" operating state can be assigned to this third switching state. The undercarriage can then be operated at least with two different speeds of a fixed size or else with a stepless speed setting that can be increased up to a maximum speed.

The direction of travel can also be reversed with any type of motor if the running gear is to be bidirectional. In this case, the switch arrangement is equipped with either only one or with two further switch positions, so that the same possibilities with regard to the driving speed are available in every direction of travel.

The switch arrangement can be operated remotely from a higher-level process control, for example when the hoist is running in a largely automated system, or there is the possibility of transferring the switch arrangement into the different switching positions via a manually operated actuator. In the latter case, it is a push button switch arrangement, as is usually used in control bulbs of hoists.

Regardless of whether it is possible to change the vehicle speed in steps or continuously, the undercarriage or the motor has a speed sensor that is connected to the electronic control system and that transmits a signal proportional to the vehicle speed to the electronic control system.

Basically two different control systems can be used to control the main closing motor. One is a so-called leading edge control, which is advantageously used when the motor is to be fed from an AC network without prior rectification. The other option is a pulse-width modulated actuator, which however requires a DC voltage signal either at the input or in an intermediate circuit. The speed of the motor is then adjusted either by changing the phase gating or ignition angle in the phase control or the pulse duty factor in the case of pulse width modulation. In the broadest sense, the phase control can also be viewed as a kind of pulse width modulation with a fixed clock frequency, which is predetermined by the network frequency. With the equality controller with pulse width modulation, however, higher clock frequencies can be achieved, which may be advantageous when it comes to reducing the pulsed network load.

The regulation of the motor speed in a motor with a main closing characteristic can be carried out either with the aid of a proportional regulator or with the aid of an integral regulator. The latter has the main advantage that no residual error remains when the leveling is corrected.

Although the controller can be constructed at any time using discrete physical components, it is expedient to implement the controller on the basis of a microprocessor, which means that the controller itself works incrementally. However, with such a digitally implemented controller, control characteristics can be generated that are difficult or impossible to implement with discrete components. In particular, with the help of a digital controller, certain unpleasant properties of integral controllers, such as slow response or starting with the wrong initial value, can be easily eliminated.

For example, it has proven to be advantageous if an initial value is assigned to the controller, which inevitably comes into effect when the undercarriage is started from a standstill. This initial value does not necessarily have to be identical to the steps by which the value of the controller or the state of the controller is incremented if, after the first switching on of the operation, the desired control in the sense of keeping the speed constant or reaching a desired speed is activated is.

Since usually the current flow angle becomes larger faster than the undercarriage can accelerate, the current flow angle will be larger when it reaches the nominal speed than is necessary to keep this speed reached constant. In order to suppress a strong overshoot of the vehicle speed, which can be caused by the time constant of the controller, the state of the controller after the first exceeding of the set speed is expediently reduced by a value which in turn is expediently greater than the incremental value with which the controller otherwise works in normal operation.

In other words, the controller works with different or larger jumps than in normal operation, if one Operational situation change occurs, which is ultimately caused by a change in the switch position.

If the running gear is to work with a largely infinitely variable driving speed, a setpoint generator is used, which can assume different values depending on the switch position. In the case of acceleration from standstill or an existing driving speed, the setpoint generator is set to a value that corresponds to the maximum possible or a higher speed. As soon as the user or the system controlling the hoist at a higher hierarchical level recognizes that the desired driving speed has been reached, the value of the setpoint generator is converted to the current speed value, so that the controller can orientate itself from this setpoint until the next adjustment is arranged becomes. The same applies, of course, in the case of a delay, i.e. the decrease in driving speed towards a lower speed.

For the rest, further developments of the invention are the subject of dependent claims.

• Fig. 1 eine Prinzipdarstellung für ein Fahrwerk mit Asynchronmotor, um Pendelungen der Last weitgehend zu unterdrücken,
• Fig. 2 eine Prinzipdarstellung für ein Fahrwerk mit Motor mit Hauptschlußcharakteristik, um Pendelungen der Last zu unterdrücken,
• Fig. 3 ein Schaltbild für das Antriebssystem nach Fig. 2,
• Fig. 4 ein Flußdiagramm für die Steuerung des Fahrwerks nach Fig. 2 und
• Fig. 5 Diagramme für den Stromflußwinkel und die Fahrgeschwindigkeit bei unterschiedlichen Betriebssituationen.

Exemplary embodiments of the subject matter of the invention are shown in the drawing. Show it:

• 1 is a schematic diagram for a chassis with an asynchronous motor to largely suppress oscillations of the load,
• 2 shows a schematic diagram for a chassis with a motor with a main closing characteristic in order to suppress oscillations of the load,
• 3 shows a circuit diagram for the drive system according to FIG. 2,
• Fig. 4 is a flow chart for the control of the chassis according to Fig. 2 and
• Fig. 5 diagrams for the current flow angle and the driving speed in different operating situations.

Fig. 1 shows a schematic representation of a mechanical embodiment of a drive system for the carriage of a hoist, for example a trolley, as used in floor-free conveyors. The drive system has an asynchronous motor 1 which only runs in one direction, the output shaft 2 of which is mechanically coupled to a schematically illustrated freewheel 3. On the output side, the freewheel 3 is connected to an input shaft 4 of a reduction gear 5, the output shaft 6 of which is in turn non-rotatably coupled to one of the drive wheels 7. The drive wheel 7 runs on a schematically shown rail 8.

The operation of the drive device described is as follows:

If a control switch, not shown, is used to ensure that the drive motor 1 is supplied with electrical energy, it begins to rotate, specifically with the design direction of rotation. He drives the input shaft 4 of the transmission 5 via the freewheel 3, which in this direction is non-positively coupled, and which then sets the drive wheel 7 in motion. As a result of the relatively large starting torque of the asynchronous motor 1, the chassis is accelerated relatively abruptly. This strong acceleration cannot be followed by the load hanging on the load suspension device in the form of a rope or a chain, which is why it will initially lag behind the running gear. After a time dependent on the conditions, the asynchronous motor 1 reaches its nominal speed, which means that from now on the running gear will travel along the running rail 8 at a constant speed. The load initially lagging the movement of the undercarriage forms a pendulum under the undercarriage traveling at constant speed, which is deflected by the jerky approach movement and which swings with its own time constant, that of the extended length of the load handler and the mass of the attached load. According to this time constant, after a corresponding travel distance of the running gear, the load oscillating in the driving direction will catch up with the running gear, in the sense that the load is located directly under the running gear. Up to this point, the oscillating load has exerted a decelerating force on the chassis. Starting from the moment the load is under the chassis and from now on, as the load overtakes the chassis in the sense of hurrying ahead, the load will exert a tractive force on the chassis that tends to accelerate the chassis.

The asychnron motor 1 cannot follow this acceleration because it can accelerate at most up to the synchronous speed, which in practical operation is only a few percent below the load speed that occurs when driving the undercarriage. The freewheel 7 disengages in this operating situation and thus makes it possible to follow the chassis of the load swinging forward. The load swinging forward will feed part of its pendulum energy into the chassis as propulsion energy. The result is that the pendulum formed by the load at the turning point is not as far from the zero position in which the load would be located directly under the chassis as would be the case if the drive train between the wheel 7 and the engine 1 would not have disengaged. As a result of the automatic disengagement of the freewheel 3, the undercarriage that has been pulled by the load has absorbed part of the pendulum energy.

As a result, the entire pendulum energy can be damped out in a few pendulum cycles without the need for control measures. The pendulum damping takes place during the forward swing, ie the half of the oscillation in which the load strives to lead the undercarriage because during this half-wave the pendulum energy is converted into driving energy for the undercarriage. The motor 1 itself does not deliver any propulsion energy during this phase. Since the pendulum must always swing symmetrically to the zero position (it cannot always be at an angle in space), the amplitude in the backswing is at most as large as the amplitude in the last forward swing.

Without the freewheel 3 located in the drive train between the engine 1 and the drive wheel 7, such an effective pendulum damping would not come about, because then the pendulum would be suspended rigidly and could not transmit any energy in its suspension. The situation is different when using the freewheel 3, as a result of which a drive arrangement is obtained which would correspond to a pendulum suspended in a damped manner.

The purely mechanical solution shown in FIG. 1 is preferably suitable for monorail overhead conveyors in which the trolleys always run in the same direction along a closed path. If a reversal of the direction of rotation is required, the freewheel 3 would have to be reversed in its direction of action in accordance with the direction of travel and in such a way that a force acting on the chassis in the direction of travel must be able to actually accelerate the chassis while uncoupling from the motor 1.

2 shows an embodiment of the new drive device, in which mechanical freewheel 3 is, as it were, electrically simulated.

The drive motor in the embodiment according to FIG. 2 is a universal motor 9 working in the main closing operation, consisting of an armature 11 and an associated field winding 12. The armature 11 is connected to a phase conductor 13 of an AC network with a connecting terminal, while another connection of the armature 11 to a End of the field winding 12 is connected. The other end of the Field winding is connected to another phase conductor 15 or a neutral conductor of the AC network via a triac 14. The armature 11 drives an input shaft 16 of a reduction gear 17, the output shaft 18 of which is in turn non-rotatably connected to the drive wheel 7 of the undercarriage.

The triac 14 is controlled by means of an electronic control device 19, the output 21 of which delivers trigger pulses to the gate of the triac 14. The controller 19 has an input 22 which is connected to a speed sensor 24 via a connecting line 23. The speed sensor 24 is rotatably coupled to the armature 11.

The control 19 is actuated by a schematically indicated switch arrangement 26 connected to an input 25. This switch arrangement 26 can optionally be a manually operated push-button arrangement or they can also represent signals that come from a higher-level control and actuate or control the control 19. For the sake of simplicity, it is assumed that these are hand switches that are operated by the user of the lifting device in question.

The operation of the arrangement according to FIG. 2 is explained below, namely on the assumption that the switch arrangement 26 only knows two switching positions, namely a neutral or zero position and a driving position.

In the neutral or zero position, the controller 19 does not emit any trigger pulses to the triac 14, which is why the circuit leading through the motor 9 remains interrupted.

If the user wants to start the gear of the hoist, he actuates the key switch 26, ie he brings the switch into the driving position. The controller 19 thereby receives a corresponding signal and at its input 25 from then on it supplies trigger pulses synchronized with the AC voltage of the network to the gate of the triac 14 in a known manner. With each first firing pulse for the triac 14, it goes into the conductive state and remains conductive until the AC mains voltage and, associated with it, the current through the universal motor 9 disappears. The triac 14 extinguishes at this point in time and remains blocked during the next half-wave until it receives a renewed ignition pulse from the controller 19 at its gate.

The relative position of the ignition pulses in relation to the preceding zeros of the AC mains voltage, also called phase angle or ignition angle, determines what power the universal motor 9 can draw from the network. The controller 19 acts as a controller and regulates the phase gating or ignition angle in the sense of stabilizing the speed of the universal motor 9, for which purpose it detects its armature speed via the speed sensor 24. The controller 19 is thus, in the broadest sense, a controller which, with a corresponding signal at its input 25, adjusts the electrical power supplied to the universal motor 9 in such a way that the universal motor 9 runs at a predetermined speed.

Because of this behavior of the controller 19, the phase angle for the universal motor 9 becomes small and, consequently, the current flow angle becomes large when the motor is loaded and its speed threatens to decrease or, conversely, the phase angle becomes large and thus the current flow angle becomes small when the speed of the universal motor 9 wants to rise because of acceleration or relief.

The assumed user has brought the push button switch 26 into the driving position when the running gear is stationary. Since the controller 19 receives the speed zero from the sensor 24, it will initially operate the triac 14 with a very small phase angle, so that the universal motor 9 can draw a lot of electrical power from the network to accelerate the chassis. To the extent that its speed approaches the target speed, the controller 19 begins to increase the phase angle, which leads to a reduction in the power consumption from the network until the nominal speed is reached.

As already described above, the load will lag the chassis due to the start-up process, i.e. the pendulum formed by the load is deflected against the direction of travel. As soon as the universal motor 9 has reached its nominal speed, which is adjusted with the aid of the control 19, the further acceleration of the oscillating load stops. The pendulum vibration will now take place in the direction of travel. As soon as the pendulum formed by the load has exceeded its zero position, at which the load is located directly vertically under the chassis or, in other words, the load handler is aligned parallel to the gravity vector, and begins to run ahead of the chassis in the direction of travel, the load is aimed to pull the landing gear behind you. The electrical properties of the universal motor 9 working in the main closing operation in connection with the control 19 now act as in the embodiment according to FIG. 1 of the freewheel 3 in that they enable the undercarriage to be driven by the load. The leading load wants to pull the chassis and thus leads to an output-side relief of the motor 9, which consequently has to deliver less drive energy.

This less drive energy would not be effective without the intervention of the controller 19, but the universal motor 9 would further increase its speed when the load was removed if the power from the power supply remained constant beforehand. The regulation by the controller 19 counteracts this, however, in the sense that it increases the phase angle by such an acceleration of the undercarriage, which would result from the interaction of the forwardly swinging load and the drive motor. Since the universal motor 9 now provides less drive power, the energy necessary for driving has to be fed from the pendulum energy and, in addition, the undercarriage continues to run on the load, which means that the pendulum is damped during the phase of the forward swing.

The main closing characteristic of the universal motor 9, which has a hyperbolic speed-torque characteristic curve and at which there is no limit speed above which it could act as a generator and thus brake the chassis, has a significantly supporting effect. Any stabilization of the driving speed in the sense of a clamping of the driving speed would prevent the sway damping. However, since the main tail motor cannot act as such a brake, the load swinging forward in the direction of travel, overtaking the undercarriage, is able to drag the undercarriage behind it, thereby reducing the amplitude directed towards the front. In this case, forward-looking amplitude is to be understood as the maximum deflection in the reversal point relative to the zero position. In the zero position, the load is located directly under the chassis and the load suspension device, i.e. the rope or chain, runs parallel to the gravity vector.

A major advantage of the arrangement according to FIG. 2 is that no mechanical freewheel is required, but that relatively cheap and space-saving electronic components are used to emulate the freewheeling characteristic. The distances that a trolley must travel during its life are not so large that the commutator present in a universal motor and its life would be an impairment.

Furthermore, by adding another switch set, the direction of rotation of the universal motor can be changed at any time, which makes journeys in both directions possible. For this purpose, it is sufficient if the field winding 12 is electrically connected to the armature 11 in a known manner via a pole reversing device, as shown in FIG. 3, in order to change the direction of rotation of the universal motor 9. With the help of such a supplement, the undercarriage can optionally be started in both directions, the pendulum-damping properties of the new drive concept being effective in both directions.

Finally, an essential advantage of the arrangement according to FIG. 2 is that undercarriages with several speeds or also stepless speed setting can be realized in a comparatively simple manner, as will be explained below.

For this purpose it is assumed that the controller 19 is a microprocessor which is able to deliver the desired mains-synchronized ignition pulses at its output 21 to the triac 14 and which is also connected via its input 25 to a switch set. As before, this switch set has a neutral or zero position, a first switch position, which corresponds to a creep speed, and a second switch position, which corresponds to the rapid speed, the chassis running in the same direction in both switch positions. There are also a third and a fourth switch position, which are used to move the undercarriage in the opposite direction at normal or rapid speed.

FIG. 3 shows the associated basic circuit diagram, namely that switch positions I to IV are each assigned a separate switch set, while the zero or neutral position corresponds to an operating situation in which all switches are open at the same time.

To the extent that components already described in the circuit arrangement according to FIG. 3 recur, they are provided with the same reference symbols and are not described again.

In the arrangement according to FIG. 3, the field winding 12 is located in the series circuit consisting of the armature 11 and the triac 14 via a reversing switch 28 actuated by a relay winding 27. which are not included for the sake of simplicity, since they are not important for understanding the invention.

The switches corresponding to the individual switching states, which are designated I to IV, are connected to the input 25, which has four individual lines which are separate from one another. They should represent the different signal states at the input, whereby the above assignment applies. These switches I to IV are connected at one end to a positive DC supply voltage U.

In addition to the exemplary embodiment according to FIG. 2, the controller 19 has a further output 29, via which the relay winding 27 is controlled, so that the direction of rotation of the universal motor 9 can be changed.

With the help of the microprocessor implementing the controller 19, a PI controller 31, a setpoint / actual value comparator 32 and a switchable reference 33 are implemented.

One input of the target / actual value comparator 32 is connected to the input 22, while the other input is connected to an output 34 of the reference. The output signal obtained from the comparator 32 reaches an input 35 of the PI controller 31, which is at an input 36 as well as the reference at its input 37 is controlled via signals coming from the input 25.

The PI controller 31 finally has an output 38, which is connected to the output 21 of the controller 19.

The functions of the reference 33 of the comparator 32 and of the PI controller 31 are implemented by program sections in the microprocessor. FIG. 5 shows the flowchart which illustrates that section of the overall program of the microprocessor which is implemented for the desired control of the motor 9. With the aid of this program according to the flow chart according to FIG. 4, the device works as follows:

As long as none of the switches I to IV is actuated, the flow chart shown in FIG. 4 is not followed. It is only when one of the switches I to IV is actuated or a corresponding control signal is supplied that the microprocessor starts a program corresponding to the flow chart in FIG. 4. The program begins at 41 and asks at a program point 42 which switch I to IV is actuated. This actuation state is stored and the program then continues in order to query the input 22 at 43, at which a signal characterizing the speed of the universal motor 9 is delivered by the speed sensor 24. The actual speed v _ist is stored and the program continues to the program point 44, at which a reference speed is generated, with which the actual speed is compared.

The parameters for this ramp generator for guiding the actual speed are the operated switch and the time that has elapsed since the switch was operated. For the further description it is assumed that the switch I a normal speed in the forward direction, the switch II a rapid speed in the forward direction, the Switch III a normal speed in the reverse direction and the switch IV the rapid speed in the reverse direction are assigned.

Depending on which of these switches has been operated, the ramp generator gradually runs up to a speed corresponding to normal speed or to a speed corresponding to rapid speed during several program runs.

After the definition or update of the command variable V _should , a _query is made at the branching point 45 as to whether the state at the input 25 has changed at this point since the last run or whether the switch position has been changed or whether the reference value has been changed for the first time after a previous switch change V _{is said to have been} exceeded.

For the further explanation it is assumed that the switch I was actuated for the first time, which corresponds to a start from standstill and an acceleration up to normal speed. The program therefore goes to the branching point 46, at which it is checked whether no switch actuation has been changed from the state to the switch actuation of switch I or switch II. For the reverse direction, the values III and IV apply accordingly at the point. If this test is positive, i.e. a change of state has taken place that corresponds to an acceleration from standstill, the program goes to an instruction block 47, in which an integral part φ for the current flow angle is set to a predetermined start value φ _s1 . This means that a fixed current flow angle is set for the start-up phase from standstill, which corresponds to a largely jerk-free but sufficiently fast start-up from a standstill.

The program then continues at an instruction block 48. At 48, the program calculates the difference between the reference value v _soll and the actual speed v _ist and obtains a control deviation parameter p from this.

This calculation branches at 49, depending on whether the system deviation parameter p is greater than zero or not. If the control deviation parameter p is greater than zero, this means that the actual speed is still lower than the target speed or the electrical power supplied to the universal motor 9 is not yet sufficient to bring the travel drive to the desired speed. Therefore, the current flow angle φ is increased by a Δ in an instruction block 51 and stored again. The incremental value Δ itself can be its function of the control deviation parameter p or else constant.

Since the controller 31 acts as a PI controller, a proportional component must also be added to the current flow angle φ, which represents the integral component. The actual current flow angle α is obtained from this by adding the control deviation parameter p or a variable derived from it to the integral component φ of the current flow angle.

After the current flow angle α consisting of the integral and the proportional portion has been calculated in this way, the current flow angle α is converted at 52 into the point in time at which, based on the preceding zero of the mains AC voltage, the ignition pulse for the triac 14 must be delivered in order to to get the desired current flow angle. The program then returns to block 42 and checks whether the position of switches I to IV has changed in the meantime. Suppose there was no change observed, the state stored on the switch operation is retained and the program can again at 43 the actual speed _v query and update the corresponding memory variable.

Since, as mentioned, the parameter for the desired speed v _{soll is} increased in time up to the value that corresponds to the switch actuation I or II or III or IV in question, the value of the command variable v _soll increases gradually during successive runs.

As provided above, the switch operation had not been changed and also there is the landing gear is still in the acceleration phase, _ie v is smaller than the predetermined switch operation by the target speed. The program will therefore continue directly through the block 48 and in block 51 the integral component φ incremental increase of the flow angle, while on the other hand, the deviation parameter p becomes gradually smaller, because the difference between V and _{V should} be reduced accordingly.

After a large number of runs have been carried out in the manner described, the point in time will come at which the ramp generation will provide a reference value v _soll which is equal to the target speed at which the undercarriage is to travel in accordance with switch actuation I. From then on, the ramp generator at 44 provides a constant reference value v _soll long change until the switch positions at the entrance 25th

During the acceleration phase, the situation is the reference speed v _soll is also after several iterations of the program loop described above occur the first time that the actual speed _v exceeds. In general, the current flow angle α is greater than it _is v for driving with constant speed is required at this time because of the previous acceleration phase, although now the proportional component P is almost become zero. These Controller situation with too large an integral part φ would lead to an undesirable overshoot in the driving speed, which is why the program does not go directly to block 48 at 45, but continues after comparing the desired value with the actual value in the left part at 53, where one Branch to an instruction block 54 is provided. In the instruction block 54, the integral component of the current flow angle φ is abruptly reduced by a larger amount than Δ by subtracting a fixed quantity K ₁ from the integral component of the current flow angle φ. After this arithmetic operation, the program continues at 48 as described.

If the next time through the loop, the actual speed is still higher than the target rate is now at the branch point 45 again as originally continued at 48, because it is not is the first exceeding the reference value v _should after a previous change in the switch positions. Since the actual speed is still greater than the target speed in this operating situation, the control deviation parameter will be negative, which is why the program after the branch point 49 does not go to the instruction block 51, but to an instruction block 55. In this instruction block 55, the integral component of the current flow angle φ becomes incremental reduced by Δ, which in turn can be a function of p or has a constant value. In the next line, the integral component φ is reduced by the amount of the control deviation parameter p or a quantity derived therefrom in order to obtain the actual current flow angle α, which is then converted again at the program point 52 into the correspondingly distorted ignition pulse.

In the stationary phase, the program outlined in FIG. 4 continues to be run continuously, the driving speed constantly oscillating around the desired speed, which is why the program after branch 49 will continue alternately via instruction block 51 or instruction block 55.

The free-wheeling characteristic mentioned at the outset is realized by the fact that the set speed is exceeded during the swinging of the load and thus during the towing of the chassis by the swinging load, which leads to the PI controller running via the instruction block 55 and increasingly reducing the integral component φ . The current flow angle becomes correspondingly smaller, i.e. the propulsion energy for the chassis comes from the pulling load.

To stop the undercarriage, the user releases all switches, which ends the run of the program according to FIG. 4.

In addition to the functions described, a number of other variants must also be taken into account. A variant is the actuation of switch II, ie starting and then accelerating up to the rapid speed. This measure is essentially only noticeable in the area of the setpoint generator at 44, insofar as the reference parameter V _{soll is increased there} up to the target speed corresponding to the rapid speed. Otherwise, the program behaves as previously described, because it starts at the first start, starting from state zero, as before via branch point 46 and instruction block 47.

The next variant that has to be taken into account is the actuation of switch II after switch I has already been actuated and the undercarriage is traveling at normal speed. This corresponds to an acceleration from normal speed to rapid speed.

In order to avoid the uncomfortable slow control characteristics of the integral controller, the program runs at the first run after actuation of switch II following branch 45 to a branch point 56, to which an instruction block 57 follows, where the integral component φ jumps by a constant K _{2 is} increased. The program then behaves as described at the beginning.

The last variant to be observed consists in switching back from switch position II to switch position I, i.e. slowing the driving speed from the rapid speed to the normal speed. During the first loop run after such a change of state, the program goes at branching point 45 in the left branch according to FIG. 4 to a branching point 58, in which it is checked whether the actual speed is greater than the target speed, which is usually always the case when switching back , whereupon an instruction block 59 returns to the normal part of the program to instruction block 48. In the instruction block 59, the integral component φ is set to a new initial value φ _S2 , which is smaller than that corresponding to driving at normal speed.

How the switch positions III and IV are to be implemented in reverse operation is known to the person skilled in the art and therefore need not be described in more detail. The control program, however, is the same as that explained in connection with switch positions I and II.

Apart from a gradual change in the driving speed, it is also possible to vary the driving speed continuously. In this case, a program according to the flow chart of Fig. 5 is used. If branch points and instruction blocks already explained occur here, they are the same Reference numerals as in the flow chart of Fig. 4 provided and not described again.

The main difference is that switch position I or switch position III corresponds to a state in which the undercarriage should continue to travel at the travel speed reached at the switchover time. Switch position II and, accordingly, switch position IV, on the other hand, mean starting or accelerating the vehicle as long as this switch state is maintained or a maximum permissible driving speed has not yet been exceeded.

Taking these changed meanings of switch positions I to IV into account, the program works as follows:

To start from standstill, the user must reach switch position II or IV, which means that in the ramp generator the reference value V _{soll is set} to a maximum of V _max in the course of several loop runs. To this extent, this behavior at block 44 corresponds approximately to the behavior of block 44 according to FIG. 4.

Since the vehicle was started from a standstill, that is, switch II was actuated for the first time, the program branches at query point 45 into the left part to an query point 61, which essentially corresponds to query point 46 according to FIG. 4. If the condition forming the criterion there is met, the integral component φ of the current flow angle is set to a start value φ _s1 and the program continues with the instruction block 48, from where it behaves exactly as explained in connection with FIG. 4 .

Assuming during the acceleration phase that the user determines that the undercarriage is now moving at the desired speed, then he will be in the Switch over state I. The result of this is that the ramp generator 44 branches out at 62 in such a way that the measured current value V act _is adopted as the reference value V _soll . In other words, the current driving speed reached at the time of the changeover becomes the reference value around which the driving speed is to be adjusted in the future. However, this update or transfer only takes place if the program recognizes the switchover from state II to state I, but not if state I continues.

The changeover from state II to state I is again recognized at branching point 45, whereby the program in turn branches into the left branch and runs to query point 63. Here the program causes the integral component φ to be abruptly reduced by a constant K ₂ , because during the preceding acceleration phase the current flow angle has reached values which are greater than are required for driving at the constant speed. The abrupt change in the integral component φ avoids an unnecessary overshooting of the driving speed when switching back from state II (= accelerating) to state I (= maintaining speed). The controller swings in faster.

After the sudden change in the integral component φ in block 64, the program returns to instruction block 48 and otherwise behaves as described in detail in connection with FIG. 4.

If acceleration is to continue from the held speed, this only has an effect on the behavior of the ramp generator at 44 insofar as the reference value is increased again to the maximum speed. The further consequence is that after branching at 45 a query 65 is reached which leads to an instruction block 66 which ensures that the integral component φ is suddenly increased to φ _S2 so that rapid acceleration can be achieved.

The program according to FIG. 5 then behaves in exactly the same way as the program according to FIG. 4 when the reference speed is exceeded.

A travel drive for a trolley of hoists has a drive train that shows a free-wheeling characteristic with respect to the direction of travel. This has the consequence that a load oscillation can be damped out quickly, because during the half oscillation of the load oscillation, in which the load leads the running gear, the running gear is not kept constant. Rather, the oscillating load is able to accelerate the chassis behind it and in this way convert pendulum energy into driving energy.

Claims (29)

Electric drive for trolleys for hoists,
with an electric drive system (1, 3, 9) which is gearingly connected to at least one wheel (7) of the undercarriage and which has means (19) which at least approximately give the drive system (1, 3, 9) a free-wheeling characteristic, in in the sense that in the case of an external force which tends to accelerate the undercarriage, there is essentially no transmission of power from the drive system (1, 3, 9) to the wheel. Electric drive according to claim 1,
with at least one electric motor (9), which is gearingly connected to at least one drive wheel (7) of the undercarriage and essentially has the characteristics of a main closing motor,
with at least one signal generation arrangement (26), which has at least a first (0) and at least a second (I, II, III, IV) state, the first state (0) of switching off the power supply to the universal motor (9) and the second state (I, II, III, IV) corresponds to the possible power supply (driving position) to the universal motor (9),
with an electronic control (19) to which the signal generating arrangement (26) is connected and which has an electrically controllable switch (14) located in a power supply line to the universal motor (9), the electronic control (19) in a first state controllable switch keeps turned off when the signal generation arrangement (26) is in the first state (0), and in a second state actuates the electronic switch (14) in the sense of stabilizing the driving speed when the signal generation arrangement is in the second state (I, II, III, IV) is located. Electric drive according to claim 2, characterized in that the electric motor (9) is a main closing motor. Electric drive according to claim 2, characterized in that the signal generating arrangement (26) has at least a third switching state (II) in which the power supply to the universal motor (9) is possible. Electric drive according to Claim 2, characterized in that the electronic control (19) has a third operating state in which it actuates the electronic switch (14) in the sense of accelerating the universal motor (9). Electric drive according to Claim 2, characterized in that the electronic control (19) actuates the electronic switch (14) in the sense of keeping a first speed constant when the signal generating arrangement (26) is in the second position (I), that the signal generating arrangement (26) has a third operating state (II), and that the electronic control (19) actuates the electronic switch (14) in the sense of keeping a second speed constant when the signal generating arrangement (26) is in the third position (II). Electric drive according to claim 5, characterized in that the second speed is greater than the first speed. Electric drive according to claim 2, characterized in that the electronic control (19) has means (27, 28) for reversing the direction of rotation of the universal motor (9). Electric drive according to Claim 7, characterized in that the signal generating arrangement (26) has a fourth state (III) which corresponds in terms of function to the second and which is assigned a reverse direction of rotation of the universal motor (9). Electric drive according to claims 3 and 7, characterized in that the signal generating arrangement (26) has a fifth switch position (IV) which corresponds functionally to the third switch position (II) and which is assigned a reverse direction of rotation of the universal motor (9). Electric drive according to claim 2, characterized in that the signal generation arrangement is a switch arrangement (26). Electric drive according to Claim 2, characterized in that the switch arrangement (26) is assigned an actuating element which can be operated manually. Electric drive according to claim 12, characterized in that the first state of the switch arrangement (26) corresponds to a neutral position of the actuating member. Electric drive according to claim 12, characterized in that the second, the third and, if present, the fourth and the fifth additional (I, II, III, IV) of the switch arrangement (26) correspond to deflected positions of the actuating member, the second and, if present the fourth state (I, III) is closer to the neutral position (O) than the third and, if present, the fifth state (II, IV). Electric drive according to claim 2, characterized in that the universal motor (9) or the running gear is assigned a speed sensor (24) which is connected to the electronic control (19) and transmits a signal proportional to the driving speed to the electronic control (19). Electric drive according to claim 2, characterized in that the electronic control (19) contains a phase control. Electric drive according to Claim 2, characterized in that the electronic switch (14) is supplied with a chain of pulses when the chassis is driven by power, the pulse duty factor of the pulse chain being dependent on the speed selected via the signal generation arrangement (26), the driving resistance and the pedal position depends on the load hanging on the hoist. Electric drive according to Claim 2, characterized in that the electronic control (19) contains a regulator (31) with a proportional characteristic. Electric drive according to claim 2, characterized in that the electronic control (19) contains a controller (31) with integral characteristics. Electric drive according to claim 18 or 19, characterized in that the controller (31) has an initial value (φ _S1 , φ _S2 ) which corresponds to a predetermined duty cycle of the pulse chain or current flow angle. Electric drive according to Claim 18 or 19, characterized in that the controller (31) operates incrementally and in that a current flow angle or duty cycle corresponds to each state of the controller (31). Electric drive according to Claim 21, characterized in that, when the operating situation changes, for which a change in the state of the signal generating arrangement is the cause, the state of the controller is suddenly changed at least once, in deviation from its normal operation. Electric drive according to Claim 22, characterized in that the abrupt change consists in the electronic control (19) setting the controller (31) to the initial value (φ _S1 , φ _S2 ) when (i) the undercarriage is started from a standstill or (ii) when switching back from a second speed to the first speed a predetermined speed has been reached. Electric drive according to Claim 23, characterized in that the electronic control (19) has at least one setpoint generator (33, 44) and that the electronic control (19) has means (32, 48) which adjust the speed of the universal motor (9) Compare the proportional signal with the setpoint (v _soll ) and that the controller (31) incrementally increases the current flow angle until the speed has become greater than the setpoint (v _soll ). Electric drive according to Claim 22, characterized in that the electronic control has at least one setpoint generator (34, 44), that the electronic control (19) has means (32, 48) which also include a signal proportional to the speed of the universal motor (9) compare the setpoint (v _soll ), and that the sudden change is that when the setpoint (v _soll ) is exceeded for the first time after an acceleration phase, a predetermined increment (K) is subtracted from the value of the controller (φ), which differs from the Increments (Δ) differ in normal operation. Electric drive according to Claim 1, characterized in that the electronic control (19) has at least one setpoint generator (34, 44), that the electronic control (19) has means (32, 48) which adjust the speed of the universal motor (9) Compare the proportional signal with the setpoint (v _soll ) and that a controller (31) incrementally reduces the current flow angle until the speed has become less than the setpoint (v _soll ). Electric drive according to Claim 4, 9 or 10, characterized in that the setpoint generator (34, 44) is set to a value which corresponds to a maximum possible or greater speed when the signal generation arrangement (26) is in the third or fifth state (II, IV) and that the set indicator (34, 44) is set to a value (v _ist ) which corresponds to the current speed when the signal generating arrangement (26) from the third or fifth state (II, IV) to the second or fourth state (I, III) is switched back. Electric drive according to Claim 4, 9 or 10, characterized in that the setpoint generator (34, 44) is set to a value which corresponds to a zero speed when the signal generating arrangement (26) is brought into the first state (O), and in that the target indicator (34, 44) is set to a value (v _ist ) which corresponds to the current speed when the signal generation arrangement (26) is switched back from the first state (O) to the second or fourth state (I, III). Electric drive according to claim 1,
with at least one asynchronous motor (1), which is geared to at least one drive wheel (7) of the chassis,
with a freewheel (3) which is geared between the Wheel (7) of the chassis and the asynchronous motor (1) is arranged
with at least one signal transmitter arrangement (26) which has at least a first and at least a second state (O, I), the first state (O) switching off the power supply to the asynchronous motor (1) and the second position (I) of the possible ones Power supply (driving position) to the asynchronous motor (1) corresponds.

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