Abstract:
A method of controlling a shift of an automated group gearbox having a multi-step main transmission and a trailing two-step range group. An input shaft of the main transmission is driven by a drive device. The main transmission and a range group have synchronization devices with shift clutches. Each synchronization device, for the main transmission, has two shift positions for respective gear ratio steps and a neutral position and the range group synchronization device has only two shift positions to shift between two gear ratios steps. To accelerate range shifts, when synchronizing the range group, the main transmission input shaft is synchronized by controlling external synchronization aids to a target rotational speed at which either after the synchronization and shifting of the gear ratio step of the range group or independently from the current synchronization condition of the range group, the target gear ratio is engaged in the main transmission.

Description:
This application is a National Stage completion of PCT/EP2012/063124 filed Jul. 5, 2012, which claims priority from German patent application serial no. 10 2011 080 849.3 filed Aug. 11, 2011. 
     FIELD OF THE INVENTION 
     The invention concerns a method for a shift control of an automated group gear. 
     BACKGROUND OF THE INVENTION 
     Automated group gears have been known for a while. They are preferably used in such commercial vehicles where a high number of gears and a large total spread are required. Dependent on the desired number of gear steps, they often comprise a multi-gear main gearbox in lay-shaft design and they also have, in this flow of force, a following two-step range group in a planetary design and/or, upstream in the flow of force, a split group in lay-shaft design. The group configuration, compared to the single gearbox, enables with a comparable number of gears clearly more compact dimensions and a lower weight. Since, depending on the gear change, simple shifting is possible in a gear group and also relatively complicated combinations of gear ratio step changes in several partial gearboxes, shifting takes place preferably fully automated or partially automated. As automated shift transmissions, these group gear boxes offer, compared to manual shift transmissions, increased operating comfort while avoiding operating errors. 
     In a general shift sequence with gear ratio changes in partial gearboxes, the shift phases in the partial gearboxes take place sequentially, wherein after the load reduction at the drive motor the main gearbox is shifted into neutral, thereafter another partial gearbox will be released and after the other partial gearbox has shifted, the gear in the main transmission is shifted and is synchronized by means of a synchronizer. 
     However, the inertia of the rotating masses of the gearbox, which need to be synchronized during gear changes, create relatively long shift durations. Long shift durations develop in particular in a range shift where first a range group needs to be shifted between a lower and an upper gear range, and thereafter also the synchronization has to be achieved with a gear change of the main transmission. Shifting of the range group can hereby take a relatively long time. A range shift is therefore often considered by the driver as disturbing and can also have an effect with regard to the dynamics of the drive operation. 
     Known from the WO2008/107318 A1 is a group transmission with a main transmission, a split group and a range transmission in which the main transmission and the following range group are designed as unsynchronized and the upstream split group is synchronized. The synchronization device of the split group can be connected and disconnected from the drive motor by a separation clutch. The range group is equipped with a simple planetary gear set which can be shift between a low speed drive step, in accordance with the planetary gear ratio, and a high-speed drive step, in accordance with a direct coupling between the main transmission and output, as well as a neutral position. 
     A shift sequence diagram for this gearbox provides that, during a range shift in the main transmission and range group, in each case a change between two gear ratios steps takes place, wherein the range group and the main transmission can be shifted in opposite directions. During the shift and after disengagement of the separation clutch and the load reduction at the drive motor, the range group is shifted into neutral, so that the entire group transmission during the gear change is at least partially separated, and therefore completely free of load, from the drive motor and from the drive train at the output side, meaning from the wheels of the vehicle. Thereafter, the rotating free masses of the main transmission and the split group are slowed by means of a transmission brake to a reliable, shiftable low rotational speed for the disengagement. At the same time, the rotational speed of the motor starts to be adjusted to match the synchronous rotational speed of the target gear. The change of the gear ratio step in the main transmission and the change of the gear ratio step in the split group happen then in parallel. Thereafter, by at least partially engaging the separating clutch, the rotational speed of the free masses is accelerated to the rotational speed of the motor, in the direction parallel to the synchronous rotational speed of the target gear, and then the claw shifted range group is synchronized via a transmission main shaft. Thereafter, the new gear ratio step of the range group is actuated whereby, during a complete engagement of the separating clutch, the load increase of the drive motor starts and the gear change is therefore completed. 
     Known from EP 1 565 674 B1 is a group transmission having a main transmission, a split group and a range group, in which the main transmission is manually shifted by means of a hand shift device, and the gear ratio of the split group and the range group are preselected via the hand shift device. During a range shift, the recognition of the neutral position in the main transmission initiates the shifting of the range group. During the shift of the range group, the target gear ratio is selected in the main transmission, wherein servo assistance for shifting of the gear ratio step in the main transmission is delayed, and is preferably released only after shifting of the range group, to reduce strong shift sounds and the wear and tear. 
     SUMMARY OF THE INVENTION 
     Based on this background, the object of the invention is to present a method for controlling the shifting of an automated group gear box with synchronized partial gearboxes, which enables short shift times. 
     The invention is based on the knowledge, that in an automated group gearbox with drivingly synchronized partial gearboxes, these partial gearboxes, by the use of gearbox internal synchronisations and external synchronization tools, can be timely synchronized in parallel, and their gear ratio steps can be shifted in overlapping shift operations, by means of which significantly shorter shift times can be achieved. 
     Thus, the invention presents a method for controlling the shifting of an automated group gear box, wherein the group transmission has at least a multi-step main transmission and a two-step range group which is, when viewed in the flow of drive, downstream of the main transmission and connected therewith by a main shaft, wherein an input shaft of the main transmission can be operationally connected or is connected with a drive device and in which the main transmission and the range group have synchronization devices with shift clutches, wherein the synchronization devices for the main transmission each have two shift positions for the respective gear ratios steps and a shift position for neutral, wherein the at least one synchronization device of the range group has exclusively two shift positions for the respective gear ratios steps and where, during a range shift, in the main transmission as well and is in the range group a change takes place between two gear ratios steps. 
     To achieve the objective, the invention provides that, during a range shift while the range group is synchronized, the input shaft of the main transmission, which was previously shifted into neutral, is synchronized to a target rotational speed by controlling external synchronization aids which have an effect at the input shaft, and that after reaching the target rotational speed, selectively either after the synchronization and shifting of the gear ratio step of the range group, or independent of the present synchronization condition of the range group, the new gear ratio step is activated in the main transmission. 
     The term target rotational speed is to be understood as being the rotational speed of a range group which is established from the actual output rotational speed of the output of the gearbox with the newly shifted gear at the input of the gearbox. 
     The method enables parallel shifting sequences in group gear boxes in which at least two serially positioned gearbox groups are designed with synchronization devices. Thus, significant shortening of the total shift times can be achieved in comparison with sequential shifting group gearboxes. Basically, such gearbox groups which are serially configured and positioned cannot use their internal synchronization shift aids at the same time, if they could work against each other. However, parallel synchronization of gearbox groups is realized with the inventive method in that the front group near the motor, meaning the main transmission, is synchronized with an external synchronization aid, for instance a combustion engine and a starting clutch or separating clutch, respectively, while the rear group, meaning the range group, is synchronized through its own synchronization device. 
     In particular, the synchronized rotational speed of the main transmission may already be set during the synchronization procedure of the range group by means of the drive motor and the start clutch or separating clutch, respectively, and the new gear ratio step in the main transmission can be shifted before the completion of the synchronization procedure of the range group. It is hereby not required to completely separate the entire drive train when shifting the drive or output, respectively. Thus, the range group at the output side can be operated with a shift device without a neutral position, which has a positive effect in regard to the manufacturing cost. 
     External synchronization aids can be provided by way of a combustion engine and/or a controllable separating clutch which is positioned between the combustion engine and the input shaft of the main transmission and/or an electric machine which is operationally connected with the main transmission and/or a controllable gearbox brake and/or a controllable hydraulic pump and/or a controllable aggregate such as an auxiliary output. Basically, external synchronization aids can be any of the elements which are suitable to create positive or negative torque at the drive train. 
     Thus, the invention can also easily be used in a vehicle with a parallel hybrid drive, in which adjustment of the target rotational speed at the input shaft can take place selectively by means of an available electric machine as the drive device. 
     It needs to be noted in the use of external synchronization aids, that the general internal synchronization devices usually designed as locking synchronizers that adjust, via a friction clutch, the rotational speed of the other shift devices, and which allow the positive shift of the gear, only after the completion of the synchronization, are not unintentionally stressed or being unlocked. The torque gradients of the external synchronization aids are therefore, when the method is executed, reasonably adjusted below the torque gradients of the internal synchronizations or are limited to such a threshold. Preferably, to increase the shift safety and for the reduction of the stress of the shift elements, the synchronization torque of the external synchronization aids is reduced during shifting of the gear, 
     Basically, such external synchronization aids can also be utilized for the support of internal synchronizations in partial gearboxes, in particular then when the partial gearboxes are actuated either at the same time or overlapping within a certain time interval. 
     It can also be provided that, during the shifting of the gear ratio of the main transmission and/or during the shifting of the gear ratio of the range group, a separating clutch which was previously engaged or partially engaged needs to be temporarily disengaged or partially disengaged. Thus, the separating clutch between the motor connection and transmission input can remain completely engaged or partially engaged during the actuating procedure of the partial gearboxes or the separating clutch, which was previously engaged or partially engaged, can be disengaged or partially disengaged when the target rotational speed at the drive motor has been reached. 
     Because the target rotational speed which needs to be established, meaning the input rotational speed for the new gear which needs to be adjusted, is created through the product of the output rotational speed and the gear ratio of the targeted gear, the adjusted target rotational speed at the drive motor can deviate from the correct target rotational speed when there is inaccurate knowledge of the output rotational speed. A resulting faulty rotational speed will be thereafter compensated for by the internal synchronization of the gearbox groups, whereby the synchronization produces work and therefore it uses kinetic energy. This work can be minimized when, to overcome a possible faulty rotational speed, the internal synchronization only has to synchronize the mass inertia of the respective gearbox parts but not torque which is transferred through the separating clutch. In this case, the separating clutch can again be temporarily disengaged or partially disengage during the actuation procedure of the partial gearboxes. Also, possible shifting delays can be omitted or at least reduced. 
     The invention provides alternative possibilities to synchronize a target gear during range shifting. Thus, the method enable the possibility of making decisions with regard to which particular alternative should be used. The boundary conditions which can hereby be used are in particular the wear and tear condition of the gearbox-internal synchronizations and/or the dynamics of the drive motor during the synchronization compared to the dynamics of the gearbox-internal synchronization and/or the sound creation during the synchronization of a drive engine designed as combustion engine, due to a rotational speed gradient. 
     In a drive train, in which the synchronization of the input shaft of the main transmission can be carried out by means of the control of a combustion engine and a separating clutch, and when the range group is designed as two-stages, an embodiment of the invention can provide the following method steps:
         Disengagement of the separating clutch to the combustion engine and a load decrease at the combustion engine   Shifting of the gear ratio step of the range group and starting the change of the gear ratio step of the main transmission, as well as adjusting the rotational speed of the combustion engine towards the target rotational speed of the target gear of the range shift and the input shaft of the main transmission, through   Shifting of the main transmission to neutral,   Waiting for the main transmission to reach the target rotational speed by use of the combustion engine,   Engagement or partial engagement of the separating clutch after completing the shift of the range group,   Shift of the new gear ratio step in the main transmission   Complete engagement of the separating clutch to the combustion engine and load increase at the combustion engine.       

     Thus, the combustion engine is brought to the target rotational speed of the gear which needs to be shifted. Through the engagement or partial engagement, respectively, of the separating clutch, the input shaft is also adjusted to this rotational speed. As a result hereby, the main transmission is synchronized and prepared for the actuation of the main transmission gear ratio. Thus, synchronization of the main transmission does not have to undertake any work during the actuation of the main transmission. 
     Depending on the duration of the synchronization procedure of the range group and the dynamics of the external synchronization aids, in particular the dynamics of the system with the combustion engine and the separating clutch, the main transmission gear can be shifted immediately after the actuation of the range group, if, within the shift timing of the range group, the combustion engine has already reached the target rotational speed, or within a short wait time in the range group which has already been shifted, as soon as the combustion engine has reached the target rotational speed. The possible wait time is however in each case shorter as compared to the common, sequential shift patterns in the partial gearboxes. Thus, a significant reduction of the total shift time can be achieved and the shifting comfort can be increased. 
     Therefore, the above embodiment provides, in each case, to wait with the actuation of the main transmission until the target gear ratio of the range group has been shifted. The internal synchronization of the main transmission is hereby under much less stress. 
     The following sequence can be provided in an alternative embodiment:
         Disengagement of the separating clutch to the combustion engine and load decrease at the combustion engine   Change of the gear ratio step of the main transmission and start of the shifting of the gear ratio step of the range group, as well as starting adjustment of the rotational speed of the combustion engine to the target rotational speed of the target gear of the range shifting at the input shaft of the main transmission, through   Shifting of the main transmission to neutral   Waiting for the main transmission to reach the target rotational speed by way of the combustion engine   Engagement or partial engagement of the separating clutch;   Shifting of the new gear ratio step in the main transmission   Support of an existing synchronization procedure of the range group through the internal synchronization of the main transmission   Shifting of the new gear ratio step in the range group   Completing engagement of the separating clutch to the combustion engine and load increase at the combustion engine       

     Thus, the combustion engine is brought to the target rotational speed of the gear which needs to be shifted. By the engagement or partial engagement, respectively, of the separating clutch, the input shaft is also brought to this target rotational speed. As a result hereby, the main transmission is synchronized and the new main transmission gear ratio can be shifted from neutral without any delay. 
     If the main transmission is now shifted and the synchronization procedure of the range group has not been completed, then the internal synchronization of the main transmission works on one side and the synchronization of the range group on the other side of the transmission main shaft which is the drive system for both partial transmissions. However, since both synchronizations synchronize the main shaft of the transmission in the same direction and towards the same rotational speed, the synchronization procedure of the range group is shortened, and the selected range gearbox ratio can be shifted earlier. Thus, this results again in a shortened total shift time. 
     The method can also be executed preferably in an automated group transmission of a commercial vehicle, which has a main transmission designed with a lay shaft construction having several gear ratio steps, for instance five, which can be drivingly connected with a controllable separating clutch or starter clutch, respectively, where the range group which is designed in planetary construction follows downstream in the flow of drive, which can be shifted between a modified shift position of a gear ratio of the main transmission and a directly transferring shift position of a gear ratio of the main transmission. 
     However, it is not at all limited to such a transmission configuration or drive configuration, and can also be applied in other drive trains with at least two automated, synchronized gearbox groups which are positioned one after the other. For instance, the invention can also be applied in vehicles with a hybrid drive in such a gearbox, where an electric machine is coupled with an input shaft and the adjustment of the input target rotational speed can take place through the electric machine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To illustrate the invention, the description is accompanied by drawings. These show: 
         FIG. 1  a gearbox schematic of an automated group transmission with a main transmission and a range group, 
         FIG. 2  a flow diagram of a rang shift in the group transmission in accordance with  FIG. 1 , 
         FIG. 3  an alternative flow diagram of a range shift in the group transmission in accordance with  FIG. 1 , and 
         FIGS. 4 ,  4 A a gear diagram and a rotational speed pattern of a sequence scheme of a range shift in accordance with  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Thus, shown in  FIG. 1  is a diagram of an automated group transmission, preferably for a commercial vehicle. The gearbox comprises a main transmission HG with five gearsets for forward gears, HG 1 , HG 2 , HG 3 , HG 4 , HG 5  and a gearset for a reverse gear step RG, as well as a two-step range group GP. 
     The main transmission HG is designed as a lay-shaft transmission, with an input shaft  4  on the drive side, a main shaft  5  on the output side, and a lay shaft  6 . The transmission ratio steps of the transmission gears HG 1 , HG 2 , HG 3 , HG 4 , HG 5 , RG of the main transmission HG comprising in each case a meshing gear wheel pair, and the reverse gear step RG has as recognized an additional rotatable intermediate wheel for the rotation reversal. Such a configuration is already known. Thus, further reference numbers for the gear wheels have been omitted. 
     The gear ratio step at the input side of the highest main transmission gear HG 5  is designed as a direct drive, with a gear wheel pair which has a fixed gear that is connected in a rotationally fixed manner with the lay shaft  6  and a fixed gear which meshes with it and which is connected in a rotationally fixed manner with the input shaft  4 . The input shaft  4  can be connected, via a separating clutch or starting clutch  3 , with a driveshaft  2  of a drive device  1  which is designed as a combustion engine. The remaining gear steps HG 1 , HG 2 , HG 3 , HG 4 , RG comprise in each case a gear fixed to the lay shaft  6  and an idler gear which is rotatably positioned on the main shaft  5 . It is possible that the vehicle comprises a parallel hybrid drive having an electric machine  14  (diagrammatically shown in  FIG. 1 ) coupled to the input shaft which can adjust the target rotational speed of the input shaft. 
     The idle gears can be connected in a rotationally fixed manner with the main shaft  5  by way of synchronization devices which are designed as synchronized shift packages SP 1 , SP 2 , SP 3 , whereby these synchronized shift packages SP 1 , SP 2 , SP 3  have shift positions for two gear steps, as well as a neutral position. Furthermore, the input shaft  4  can be directly connected with the main shaft  5  by means of the synchronized shift package SP 1  in the input side for the shifting of a direct gear. 
     The range group GP is designed as a planetary transmission. It comprises a sun gear  8  which is connected in a rotationally fixed manner with the end of the extended main shaft  5 , in the direction of the downstream following range group GP, a ring gear  11 , as well as a planetary carrier  10 . which supports several meshing planets  9  between the sun gear  8  and the ring gear  11 , and which is, at the output side, connected in a rotationally fixed manner with an output or output shaft  7 . 
     The range group GP can be shifted by means of an additional synchronized shift package SP 4  between two shift positions. In a first shift position, the ring gear  11  is connected with a stationary part  12 , such as a gearbox housing, so that the transmission ratio of the planetary transmission becomes effective at the output shaft  7 . In a second shift position, the ring gear  11  is coupled with the planetary carrier  10  so that the planetary transmission rotates with the main shaft  5  as a block, and the output shaft  7  directly couples the main shaft  5 . A neutral position is not provided for the synchronized shift package SP 4  of the range group GP. Overall, the group transmission thus represents a 10-gear transmission. 
       FIG. 2  shows an example shift sequence for a range shift of such gearbox. Gear ratio changes take place in both partial transmissions HG, GP. 
     This relates, in the exemplary transmission in accordance with  FIG. 1 , to an upshift or downshift between a fifth gear G 5  and a sixth gear G 6  wherein, in the opposite shift direction, the range group GP is shifted between a lower and an upper gear range GP 1 , GP 2  and the main transmission HG is shifted between the first gear HG 1  and the fifth gear HG 5 . For the sequence which is shown in  FIG. 2 , a gear change is assumed in the following from the sixth gear G 6  to the fifth year G 5 . 
     Shifting is initiated after a request for a gear change which requires a range shift, In the beginning, the separating clutch  3  is disengaged in one step Si, and in parallel, in step S 2 , the load at the combustion engine  1  is reduced. 
     Thereafter and during step  53  and step S 4 , the change of the gear ratio of the main transmission HG and the change of the gear ratio of the range group GP are simultaneously initiated. Hereby, the main transmission HG is shifted into neutral in an intermediate step S 3   a  and remains in this position in an intermediate step S 3   b  during a wait time while the rotational speed of the combustion engine  1  is brought towards the target rotational speed of the new gear in a step S 5 . When the target rotational speed is reached, the separating clutch  3  is preferably partially engaged in an intermediate step S 3   c , and the new gear ratio is immediately shifted in the main transmission HG during an intermediate step S 3   d.    
     The shifting of the range group GP is at this time not finished and thus, the synchronized shift package SP 4  of the range group GP is still active. Since the two partial transmissions HG, GP are in a drive connection with each other through the main shaft  5 , the initiation of the main transmission HG, previously externally synchronized through the rotational speed guidance of the combustion engine  1  and the engagement or partial engagement, respectively, of the separating clutch  3 , causes its internal synchronized shift package SP 1  to become active. In the following, the synchronized shift package SP 1  of the main transmission HG and the synchronized shift package SP 4  of the range group GP are synchronizing the main shaft  5  towards the same rotational speed, whereby prior to this the calculated target rotational speed, resulting from the output rotational speed and the gear ratio of the target gear G 6 , has been adjusted. Synchronization of the range group GP is therefore rapidly completed in a step  36 , so that the range group GP can be shifted faster compared to what was possible up to now, in a step S 7  into the targeted range. Thereafter, the load increase at the combustion engine  1  takes place in a step S 8 , wherein the separating clutch  3 , which may have been previously partially engaged, will be completely engaged and the gear change is complete. 
       FIG. 3  shows an alternative shift sequence of a range shift from a sixth gear G 6  to a fifth gear G 5  for the group gearbox in accordance with  FIG. 1 . A gear diagram as well as a rotational speed diagram, are presented respectively in  FIGS. 4 and 4A . Thus, the main transmission HG is shifted from a first main transmission gear HG 1  to a fifth main transmission gear HG 5 , whereby initially the synchronized package SP 3  is shifted into neutral and after an external synchronization of the input shaft  4  through the combustion engine  1  and the initiation of the main transmission HG, the related synchronized package SP 1  of the fifth gear G 5  is moved into the respective shift position. The range group GP is hereby shifted in parallel to it, through a direct change of the shift position of the respective synchronized package SP 4  from the upper gear range GP 2  to a lower gear range GP 1 . 
     During the shift sequence in accordance with  FIG. 3 , after the disengagement of clutch  3  in step S 1  and the load reduction in the time interval Δt_lastab in step S 2 , shifting is again initiated in the range group GP, as well as shifting in the main transmission HG. The main transmission HG is hereby shifted in an intermediate step S 3   a  into neutral. For shifting the range group GP, a time interval of Δt_GP is assumed, and for the gear ratio change of the main transmission HG a time interval Δt_HG. Within the total shifting time Δt_lastfrei, the drive train has no torque. 
     During synchronization of the range group GP, the synchronization rotational speed of the main group HG is adjusted by means of the combustion engine  1  and the separating clutch  3 . Hereby, the rotational speed n_VM of the combustion engine  1  is brought to the target rotational speed n_Ziel which is reached at the time point t_synch. Herein, the main transmission HG remains in a wait position in an intermediate step S 3   b.    
     Contrary to the shift sequence in accordance with  FIG. 2 , the main transmission gear HG 5  is, however, shifted at the time when during a step  59  shifting of the range group GP into the lower gear range GP 2 −GP 1  has been completed. After this range change, the clutch  3  is engaged or partially engaged, respectively, in a step S 10  and at that time, the target rotational speed is adjusted at the input shaft  4 . The main transmission gear HG 5 , because the main transmission HG is now already synchronized via the external synchronization by means of the combustion engine  1  and the clutch  3 , can be immediately shifted in a step S 11 , meaning that the synchronization package SP 1  is brought into the respective shift position. Thus, the internal synchronization does not have any task to accomplish because the synchronization already took place when the gear was shifted. Thereafter, the load increase follows in step S 12  during a time interval Δt_lastauf, whereby the clutch  3  is completely engaged, if this did not already happen. 
     In the case that shifting of the range group GP has been completed before reaching the target rotational speed of the combustion engine  1 , the main transmission HG is immediately shifted without delay after the external synchronization. 
     REFERENCE CHARACTERS 
     
         
           1  Combustion Engine, Drive Device 
           2  Drive Shaft 
           3  Separating Clutch 
           4  Input Shaft 
           5  Main Shaft 
           6  Countershaft 
           7  Output Shaft, Output Drive Shaft 
           8  Sun Gear 
           9  Planetary Gear 
           10  Planetary Carrier 
           11  Ring Gear 
           12  Stationary Part, Transmission Enclosure 
         G 5  Fifth Gear 
         G 6  Sixth Gear 
         GP Range Group 
         GP 1  Lower Gear Range 
         GP 2  Upper Gear Range 
         HG Main Transmission 
         HG 1  First Main Transmission Gear 
         HG 2  Second Main Transmission Gear 
         HG 3  Third Main Transmission Gear 
         HG 4  Fourth Main Transmission Gear 
         HG 5  Fifth Main Transmission Gear 
         n Rotational speed 
         n_VM Motor Rotational speed 
         n_Ziel Target Rotational speed 
         RG Reverse Gear Step 
         S 1 -S 12  Shift Step 
         SP 1  Synchronization Device, Synchronization Shifting Package 
         SP 2  Synchronization Device, Synchronization Shifting Package 
         SP 3  Synchronization Device, Synchronization Shifting Package 
         SP 4  Synchronization Device, Synchronization Shifting Package 
         t Time 
         t_synch Synchronization Time Point 
         Δt_GPShift Time of Range Group 
         Δt_HG Shift Time of Main Transmission 
         Δt_lastab Load Reduction Time Interval 
         Δt_lastfrei No-Load Time Interval 
         Δt_lastauf Load Increase Time Interval