Patent Publication Number: US-2023158954-A1

Title: Adjustment device for an external vision unit of a vehicle

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Netherlands Patent Application no. 2029873 filed on Nov. 23, 2021, which is incorporated by reference as if fully set forth. 
     FIELD OF INVENTION 
     The invention relates to a device for adjusting an orientation of an external vision element, such as an external rear view or side view mirror, or camera, of a vehicle. 
     BACKGROUND 
     Adjustment devices for an external vision unit of a vehicle typically include a vision element, such as a mirror, camera, and/or display. They are configured to adjust an orientation of the vision element relative to the vehicle, typically about a horizontal and a vertical axis, such that a driver of the vehicle can fine-tune its rearward view. 
     An adjustment device can, for example be part of an external vision unit of a vehicle, wherein the vision element is often carried by a frame. The frame is adjustable relative to a base, where the base is configured to be mounted to a body of the vehicle. 
     Often, the external vision unit is further adjustable between a folded position, or park position, in which the frame extends substantially parallel to the vehicle, and an extended position in which the frame extends substantially outward from the vehicle. This operation is often referred to as power fold actuation. The power fold actuation can be driven by a dedicated power fold actuator, which is separate from a fine-tuning adjustment device for fine tuning the driver’s rearward view in the extended position of the external vision unit. 
     In some instances, an adjustment device may be arranged to fine tune an orientation of the vision element about two respective axes and drive the power fold actuation between the folded position and the extended position. Such adjustment devices may thus be regarded as conventional mirror adjustment devices with additional power fold capabilities or as conventional mirror adjustment devices having a multi-axis power fold actuator. An example of such a device is described in EP3218226, where the adjustment of the vision element is driven by two separate electromotors; a first one for adjustment about the vertical axis and a second one for adjustment about the horizontal axis. However, in such an adjustment device both electromotors need to be relatively powerful because of the relatively high clamping forces required to retain the adjustment device in an adjusted position. This increases the overall cost of the adjustment device, for example in terms of components and manufacturing, but also in terms of the overall form factor and power consumption of the adjustment device in use. Accordingly, a need exists for an adjustment device at reduced costs that can fine tune an orientation of a vision element about two respective axes and drive the power fold actuation between the folded position and the extended position using the power of a single power door control module. 
     SUMMARY 
     In an aspect, the invention relates to an adjustment device for adjusting an orientation of a vision element of a vehicle about a first pivot axis and a second pivot axis. The adjustment device comprises a base for coupling to a vehicle and a frame pivotably coupled to the base, the frame having a first frame part being pivotable relative to the base about the first pivot axis and a second frame part being pivotable relative to the first frame part about the second pivot axis. The adjustment device further comprises a drive unit for driving the frame pivotally about the first pivot axis and the second pivot axis. The drive unit comprises a first powertrain operationally between the first frame part and the base, having a first electromotor connected via a first transmission to a first driven element for driving the first frame part relative to the base about the first pivot axis, and a second powertrain operationally between the first frame part and the second frame part, having a second electromotor connected via a second transmission to a second driven element for driving the second frame part relative to the first frame part about the second pivot axis. The second electromotor has a lower power rating compared to a power rating consumption of the first electromotor. The second transmission further applies a second speed-reducing transmission ratio from the second electromotor to the second driven element, the second speed-reducing transmission ratio providing a greater speed reduction than a first transmission ratio from the first electromotor to the first driven element. 
     Hence, in an aspect, the device comprises a first powertrain, which includes the relatively high-powered first electromotor and the first transmission, dedicated for pivoting the frame about the first pivot axis, and a separate second powertrain, which includes the relatively low-powered second electromotor and the second transmission, dedicated for pivoting the frame about the second pivot axis. Accordingly, the adjustment device includes only a single relatively high-powered electromotor, which enables the adjustment device to be controlled by a modern standard door control module of a vehicle, which has only one high-power control output. The first electromotor having the high-power rating can accordingly be controlled by the only one high-power control output of the modern standard door control module, while second electromotor having the lower power rating can be controlled by a low-power control output of the modern standard door control module. 
     In an aspect, the invention relates to an external vision unit for a vehicle, comprising the adjustment device for adjusting an orientation of a vision element, as well as the vision element itself, where the external vision unit can be mounted to the frame of a vehicle. 
     In an aspect, the invention relates to an external vision unit system for a vehicle, comprising the adjustment device for adjusting an orientation of a vision element, the vision element itself, and a door control module operatively connected to the adjustment device for sending a power signal to the adjustment device. 
     In an aspect, the invention relates to an external vision unit system, comprising a door control module that provides a virtual transmission for the first powertrain, such that the first power train is selectively operable according to at least two virtual transmission ratios, each transmission ratio being associated with a different power signal than the other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It is understood, however, that the invention is not limited to the precise arrangements shown. In the drawings: 
         FIG.  1    shows an example of a prior art adjustment device; 
         FIG.  2    shows a view of the adjustment device; 
         FIG.  3 A  shows a frontal view of an adjustment device; 
         FIG.  3 B  shows a top view of an adjustment device; 
         FIG.  4    shows an example of an external vision unit; 
         FIG.  5 A  shows an example of an external vision unit system. 
         FIG.  5 B  shows an example of an external vision unit system. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     It will be appreciated that any of the aspects, features and options described herein can be combined. It will also be appreciated that any of the aspects, features and options described in view of the adjustment device apply equally to the external vision unit and external vision unit system, and vice versa. It will further be appreciated that any of the aspects, features and options described in view of the adjustment device apply equally to a vehicle. 
       FIG.  1    illustrates a prior art adjustment device  144  for an external vision unit. The adjustment device  144  comprises a base  174  for mounting to the body of a motor vehicle, such as a car, and a frame  146 ,  148  pivotably arranged about the base  174 , about a first pivot axis  150 . In this example the frame comprises a first frame part  146  and a second frame part  148  both of which are commonly pivotable about the first pivot axis  150 . The second frame part  148  is also movably coupled to the first frame part  146  such that the first frame part  146  and second frame part  148  are pivotable relative to each other about a second pivot axis  152 . In this example, the first frame part  146  is pivotable relative to the base  174  about the first pivot axis  150  and is not pivotable relative to the base  174  about the second pivot axis  152 . Further, the second frame part  148  is pivotable relative to the base  174  about the first pivot axis  150  and the second pivot axis  152 . The second frame part  148  is also pivotable relative to the first frame part  146  about the second pivot axis  152 . 
     The prior art adjustment device  144  is arranged to adjust an orientation of the external vision unit about the first pivot axis  150  and the second pivot axis  152 , using two identical relatively powerful electromotors to overcome the relatively large clamping forces required to retain the adjustment device  144  in an adjusted position. The two identical relatively powerful electromotors are omitted from  FIG.  1    to show the underlying structures, including two substantially identical transmissions  122 ,  124 , respectively associated with the two relatively powerful electromotors. Each transmission  122 ,  124  has two transmission stages between an associated electromotor output and a respective driven element  110 ,  120 . A first one of the two relatively powerful electromotors adjusts the external vision unit about the first pivot axis  150  and a second one of the relatively powerful electromotors adjusts the external vision unit about the second pivot axis  152 . That the two electromotors are required to be relatively powerful adds to the overall cost of the adjustment device, for example in terms of components and manufacturing, but also in terms of the overall form factor and power consumption of the adjustment device  144  when in use. 
       FIG.  2    illustrates a perspective view of the of the adjustment device  44  for an external vision unit. In an embodiment, the adjustment device comprises a base  74 , which may be mounted to the body of a motor vehicle, such as a car. The adjustment device  44  further comprises a frame  46 ,  48  which may be pivotably arranged about the base  74  about a first pivot axis  50 . In an embodiment, the frame comprises a first frame part  46  and a second frame part  48 , both of which may be pivotable about the first pivot axis  50 . In an embodiment, the second frame part  48  may also be movably coupled to the first frame part  46 . In this example, the first frame part  46  and second frame part  48  may be pivotable relative to each other about a second pivot axis  52 . Further, the second frame part  48  may also be pivotable relative to the base  74  about the first pivot axis  50  and the second pivot axis  52 . A vision element, such as a mirror, camera or display, may be mounted to the second frame part  48 . The vision element is omitted from the figures to show underlying components. 
     In an embodiment, the adjustment device  44  is movable between a folded position in which the frame  46 ,  48  extends substantially parallel to the vehicle, and an extended position in which the frame  46 ,  48  extends substantially outward from the vehicle.  FIG.  2    shows the adjustment device  44  in the extended position. In an embodiment, the adjustment device  44  can be moved between the folded and the extended position by pivoting the frame  46 ,  48  relative to the base  74  about the first pivot axis  50 . 
     The adjustment device  44  further comprises a drive unit, which includes two electrical actuators, for example two electromotors, namely a first electromotor  100  and a second electromotor  200 . A first powertrain  23  may include the first electromotor  100  connected by a first transmission  22  to a first driven element  10 . In an embodiment, the first driven element  10  is part of the base  74 , for example a base gearing  75  integrally formed with the base  74  or rigidly fixed to a remainder of the base  74 . In an embodiment, the first powertrain  23  is provided for pivoting the frame  46 ,  48  relative to the base  74  about the first pivot axis  50 . 
     A second powertrain  25  may include the second electromotor  200  connected by a second transmission  24  to a second driven element  20 . In an embodiment, the second driven element  20  may be part of the second frame part  48 , for example a gearing  72  integrally formed with the second frame part  48  or rigidly fixed to a remainder of the second frame part  48 . In an embodiment, the second powertrain  25  is provided for pivoting the first frame part  46  relative to the second frame part  48  about the second pivot axis  52 . 
     In an embodiment, the first powertrain  23  and the second powertrain  25  are separate from each other. 
       FIG.  3 A  shows a frontal view of the adjustment device  44 , and  FIG.  3 B  shows a top view of the adjustment device  44 . Part of the frame  46 ,  48  has been omitted in the  FIG.  3 A  to show details of the first transmission  22  and the second transmission  24 . In  FIG.  3 B , the electromotors  100 ,  200  have been omitted to show details of the transmissions  22 ,  24 . 
     In an embodiment, the first transmission  22  comprises two transmission stages: a first input transmission stage  41 , provided between an output of the first electromotor  100  and a first transmission intermediate member  43 ; and a first output transmission stage  42  provided between the first transmission intermediate member  43  and the first driven element  10 . 
     The output of the first electromotor  101  may include an output shaft  82  of the first electromotor provided with an input worm  81  of the first electromotor. In an embodiment, the input worm  81 , which is rotatably driven by the first electromotor  100  via the output shaft  82 , meshes with the first worm gear  70  to transfer torque to the intermediate member  43 . Movement of the first worm gear  70  drives movement of the intermediate shaft  11  and the first output worm  71  such that the first output worm  71  rotates together with the first worm gear  70 , and also meshes with a base gearing  75  of the base  74 . 
     In an embodiment, the first input transmission stage  41  is formed between the input worm  81  and the first worm gear  70 , and the first output transmission stage  42  is formed between the first output worm  71  and the base gearing  75 . 
     Compared to the first transmission  22 , the second transmission  24  comprises at least an additional transmission stage. In an embodiment, the second transmission  24  comprises at least two transmission stages. In an embodiment, the second transmission  24  comprises at least three transmission stages. 
     In an embodiment, the second transmission  24  comprises three transmission stages: a second input transmission stage  91 , provided between an output  201  of the second electromotor  200  and a second transmission primary intermediate member  94 ; an intermediate transmission stage  92 , provided between the second transmission primary intermediate member  94  and a second transmission secondary intermediate member  95 ; and a second output transmission stage  93 , provided between the second transmission secondary intermediate member  95  and the second driven element  20 . The output of the second electromotor  201  may include an output shaft  32  of the second electromotor provided with a second input worm  31 . The second transmission primary intermediate member  94  may include a primary intermediate shaft  60  further comprising a primary intermediate worm gear  61  and a primary evoloïd gear  62 . The second transmission secondary intermediate member  95  may include a secondary intermediate shaft  21  further comprising a secondary evoloid gear  29  and a second output worm  28 . 
     In an embodiment, the second input worm  31 , which is rotatably driven by the second electromotor  200  via the output shaft  32 , meshes with the primary intermediate worm gear  61  to transfer torque to the primary intermediate member  94 . Movement of the primary intermediate worm gear  61  drives movement of the primary intermediate shaft  60  and the primary evoloid gear  62  such that the primary intermediate worm gear  61  rotates together with the primary evoloid gear  62 . The primary evoloïd gear  62  meshes with the secondary evoloid gear  29  to transfer torque to the secondary intermediate member  95 . Movement of the secondary evoloid gear  29  drives movement of the secondary intermediate shaft  21  and the second output worm  28  such that the secondary evoloid gear  29  rotates together with the second output worm  28  and meshes with the gearing  72  of the second driven element. 
     In an embodiment, the second input transmission stage  91  is between the output of the second electromotor  200 , here an output shaft  32  provided with a second input worm  31 , and a second transmission primary intermediate member  94 , here a primary intermediate shaft  60  provided with a primary intermediate worm gear  61  and a primary evoloïd gear  62 . The primary intermediate worm gear  61  of the primary intermediate member meshes with the second input worm  31 , hence providing the second input transmission stage  91  of the second electromotor  200 . 
     In an embodiment, an intermediate transmission stage  92  is provided between the primary intermediate member  94 , here including primary intermediate shaft  60  provided with primary intermediate worm gear  61  and primary evoloid gear  62 , and a second transmission secondary intermediate member  95 , here including secondary intermediate shaft  21  provided with secondary evoloid gear  29  and a second output worm  28 . The primary evoloid gear  62  of the primary intermediate transmission member  94  meshes with the secondary evoloid gear  29  of the secondary intermediate transmission member  95 , hence providing the intermediate transmission stage  92 . 
     In an embodiment, the meshing of primary evoloid gear  62  and secondary evoloid gear  29  are effective for applying a large reduction ratio, as the primary evoloid gear  62  can be given very few teeth. In an embodiment, the primary evoloid gear  62  has only one tooth. In an embodiment, the primary evoloid gear  62  has only two teeth. In an embodiment, the primary evoloid gear  62  has only three teeth. 
     In an embodiment, a second output transmission stage  93  is provided between the second transmission secondary intermediate member  95 , here including secondary intermediate shaft  21  provided with secondary evoloid gear  29  and a second output worm  28 , and the second driven element  20 . The second output worm  28 , which rotates together with the secondary evoloid gear  29 , meshes with the second driven element  20  here a gearing  72  of the frame  46 ,  48  to provide the second output transmission stage  93 . In an embodiment, the secondary evoloid gear  29 , meshes with the second driven element  20 , here a gearing  72  of the second frame part  48 , to provide the second output transmission stage  93 . In this example, driving the second driven element  20  pivots the second frame part  48  relative to the base  74  about the second pivot axis  52 . 
     In an embodiment, the second transmission  24  may include more transmission stages than the first transmission  22 . 
     In another embodiment, the first transmission  22  comprises a single transmission stage provided between the output shaft  82  of the first electromotor  100  and the first driven element  10 . In such an embodiment, the second transmission  24  may comprise two transmission stages, three transmission stages, or any number of transmission stages such that the second transmission  24  includes more transmission stages than the first transmission  22 . Each transmission stage may particularly be a reduction stage that reduces an output speed relative to input speed. 
     Hence, the first transmission may optionally comprise at most two transmission stages, such as two, or only one transmission stage, from the first electromotor output to the first driven element. In such an embodiment, the second transmission  24  may comprise three transmission stages, four transmission stages, or any number of transmission stages such that the second transmission  24  includes more transmission stages than the first transmission  22 . Each transmission stage may particularly be a reduction stage that reduces an output speed relatively to input speed. 
     In an embodiment, the second transmission  24  comprises two transmission stages, in particular two reduction stages, for reducing an output speed of the second electromotor  200  to a reduced speed of the second driven element  20 . The second transmission  24  may comprise an input transmission stage from the second electromotor output  32  to an intermediate transmission member, e.g. an intermediate shaft; and an intermediate transmission stage between the intermediate transmission member to the second driven element  20 . 
     In an embodiment, the second transmission  24  may comprise three transmission stages, particularly three reduction stages. For example, the second transmission  24  may comprise three transmission stages as described herein: an input transmission stage  91  from the second electromotor output  201  to a primary intermediate transmission member  94 , e.g. a primary intermediate shaft  60 , primary worm gear  61  and primary evoloid gear  62 ; an intermediate transmission stage  92  between the primary intermediate transmission member  94  and a secondary intermediate transmission member  95 , e.g. a secondary intermediate shaft  21 , secondary evoloid gear  29  and second output worm  28 ; and an output transmission stage  93  from the secondary intermediate transmission member  95  to the second driven element  20 . 
     In an embodiment, the second transmission  24  applies a transmission ratio of approximately 1:8. In an embodiment, an input angular speed of about 30 degrees per second is reduced to an output angular speed of about 4 degrees per second. For such transmission ratio it may be preferred for the second transmission  24  to include at least two transmission stages, such as two transmission stages, three transmission stages, or four transmission stages. 
     The first and second electromotors  100 ,  200  may be powered by a common door control module  370  of a vehicle such that the door control module  370  can control both the first electromotor  100  and the second electromotor  200 . In an embodiment, the first electromotor  100  requires relatively high power, e.g. draws relatively high currents compared with the second electromotor  200 . The second electromotor  200  may require only a fraction of the power consumed by the first electromotor  100 . The first electromotor  100  and the second electromotor  200  may particularly be low-powered electromotors. The first electromotor  100  and the second electromotor  200  may be low-powered DC electromotors. 
     In accordance with the invention, the second electromotor  200  has a lower maximum power consumption, or power rating, compared to a maximum power consumption, or power rating, of the first electromotor  100 . In an embodiment, the maximum power consumption of the second electromotor  200  is lower than the maximum power consumption of the first electromotor  100  by a factor in the range of 2 to  20 . The maximum power consumption of the second electromotor  200  may be lower than the maximum power consumption of the first electromotor  100  by a factor of between  5  and  15 . The maximum power consumption of the second electromotor  200  may be lower than the maximum power consumption of the first electromotor  100  by a factor  10 . In an embodiment, the maximum power consumption of the first electromotor  100  may for example be between 10-20 Watt and the maximum power consumption of the second electromotor  200  may for example be between 1-5 Watt. In an embodiment, the maximum power consumption of the first electromotor  100  is about 12 Watt and the maximum power consumption of the second electromotor  200  is about 2 Watt. 
     In an embodiment, the first electromotor  100  draws between 1-2 Ampere. In an embodiment, the first electromotor  100  draws 1.5 Ampere. The second electromotor  200  may draw only a fraction of the current that the first electromotor  100  draws, for example only 50% of the current that the first actuator draws. In another embodiment, the first electromotor  100  draws at most 1 Ampere of current while the second electromotor  200  may be arranged to draw at most 0.5 Ampere of current. 
     In order to overcome clamping forces with which the adjustment device  44  is held in position after adjustment, using the less powerful second electromotor  200 , the second transmission  24  applies in comparison with the first transmission  22  an additional speed-reduction from the second electromotor  200  to the second driven element  20 . The additional reduction in speed provided by the second transmission  24  comes with an increased torque transmission from the second electromotor  200  to the second driven element  20 . The adjustment device  44  may accordingly include only a single relatively high-powered electromotor, e.g. the first electromotor  100  and one relatively low-powered electromotor, e.g. the second electromotor  200 . The second electromotor  200  having a relatively low power rating, may be less costly, and may have a smaller form factor compared to high power-rated electromotors for enabling miniaturization of the adjustment device  44 . Also, power consumption of the adjustment device  44  may be reduced. Advantageously, the adjustment device  44  may be controlled by a modern standard door control module of a vehicle, which has only one high-power control output. The first electromotor  100  having the relatively high-power rating can accordingly be controlled by the only one high-power control output of the modern standard door control module, while the second electromotor  200  having the relatively low power rating can be controlled by a low-power control output of the modern standard door control module of the vehicle. 
     In an embodiment, to account for the reduced power of the second electromotor  200 , the second transmission is operationally arranged between the second electromotor  200  and the second driven element  20 , where the second transmission  24  trades-off adjustment speed about the second pivot axis  52  for a torque increase at the second driven element  20 . 
     In an embodiment, it is acceptable to have a relatively low adjustment speed about one of the two pivot axes  50 ,  52 . In an embodiment, the relatively low adjustment speed may be about a horizontally extending pivot axis. In such an embodiment, the first pivot axis  50  may then correspond to a power fold axis, about which the adjustment frame  46 ,  48  is pivoted from a folded position to an extended position. This way, the power fold actuation can be driven by the relatively high-powered electromotor, for example the first electromotor  100 , with a relatively high adjustment speed. The first pivot axis  50  may thus for example extend vertically in use. The second pivot axis  52  may for example extend non-parallel to the first pivot axis  50 . In an embodiment, the second pivot axis  52  may extend transverse to the first pivot axis  50 . In an embodiment, the second pivot axis  52  may extend horizontally. 
     In an embodiment, the electromotors  100 ,  200  are arranged in a standing position, where the electromotor outputs are rotatably driven about parallel axes. The electromotors  100 ,  200  may extend vertically and parallel to the first pivot axis  50 . It is appreciated that other orientations of the electromotors  100 ,  200  are also possible. 
       FIG.  4    shows an example of an external vision unit  300  for a vehicle having shell-shaped cover  350  that defines a cavity  360  for holding the drive unit of the adjustment device  44 . The shell-shaped cover  350  may also cover a vision element (not shown), such as a mirror, camera, LIDAR and/or display. 
     Optionally, the frame  46 ,  48  comprises a shell-shaped cover  350  which defines a cavity  360  for holding the drive unit. In an embodiment, the shell-shaped cover  350  is part of the frame  46 ,  48 , or may be fixed or coupled thereto. In an embodiment, the shell-shaped cover  350  is integrally formed with the second frame part  48 , or may be fixed or coupled thereto. 
     In some implementations, the vision element is coupled to the frame  46 ,  48  for being adjusted about the first and second pivot axes  50 ,  52 . In an embodiment, the vision element may specifically be coupled to the second frame part  48 . The first pivot axis  50  and the second pivot axis  52  may extend non-parallel to each other. In an embodiment, the first pivot axis  50  corresponds to a power fold axis, e.g. a vertical axis, about which the external vision unit is pivoted between a folded position and an extended position. The second pivot axis  52  may be substantially transverse to the first pivot axis  50 . 
     The shell-shaped cover  350  has a proximal end  310 , in use proximate the vehicle while in use, and a distal end  320  opposite the proximal end  310 . In an embodiment, the shell-shaped cover  350  may delimit an asymmetrically shaped cavity  260 . In such an example, as illustrated in  FIG.  4   , the shell-shaped cover  350  is tapered towards the distal end  320 , primarily for improving aerodynamic properties. Hence, a tapered distal end  320  may have little room for accommodating an electromotor and transmission coupled thereto. However, in an embodiment, the first and second electromotors  100 ,  200  may be arranged adjacent each other in the cavity  360 , such that the first electromotor  100  may be accommodated in the cavity  360  nearer the proximal end  310  and the second electromotor  200 , being relatively low powered and of smaller form compared with the first electromotor  100 , may be accommodated nearer the distal end  320  of the shell-shaped cover  350 . 
     In an embodiment, an output axis of the first electromotor  102  is parallel to the first pivot axis  50 . In an embodiment, the output axis of the first electromotor  102  is parallel to the first pivot axis  50  and an output axis of the second electromotor  202  extends parallel to the first pivot axis  50 . For a particular compact setup, the second electromotor  200  may be arranged in the cavity  360  in an orientation where the output axis of the second electromotor  202  extends transverse to the first pivot axis  50 , e.g. parallel to the second pivot axis  52 . In an embodiment, the output axis of the first electromotor  102  is parallel to the first pivot axis  50  and an output axis of the second electromotor  202  extends parallel to the second pivot axis  52 . 
     In an embodiment, the second electromotor volume is smaller than the first electromotor volume by a factor of between 1.1 and 4. In an embodiment, the second electromotor volume is 50% less than the first electromotor volume. The saved space from the smaller electromotor  200  may, for example, be occupied by additional components of the second transmission  24  for providing a suitable speed reduction ratio. These additional components may include additional intermediate members forming additional transmission stages. These additional components may also include additional gearings or evoloid gearings having varying numbers of teeth accordingly. 
     The adjustment device  44  is movable between a folded position, in which the frame  46 ,  48  extends substantially parallel to the vehicle, and an extended position in which the frame  46 ,  48  extends substantially outward from the vehicle. The adjustment device can be moved between the folded and the extended position by pivoting the frame  46 ,  48  relative to the base  74  about the first pivot axis  50 . 
     The external vision unit  300  may be part of an external vision unit system  400  of a vehicle  371  as exemplified in  FIGS.  5 A and  5 B . The system comprises the external vision unit  300  and a control module, particularly a door control module  370  of the vehicle  371 . The door control module  370  is connected for controlling an orientation of the external vision unit  300  relative to the vehicle  371 . The door control module  370 , may be connected to the adjustment device  44  to send a power signal to the adjustment device  44 . 
     In an embodiment, the door control module  370  may be arranged to send a power signal to the adjustment device  44  for powering the first electromotor  100  and/or the second electromotor  200 . The door control module  370  may for example send a high-power signal  5  to the first electromotor  100  of the external vision unit  300 , and a low-power signal  6  to the second electromotor  200  of the external vision unit  300 . 
     In an embodiment, the door control module  370  may for example be configured to selectively send a first power signal to the first electromotor  100  for operating the first electromotor  100  at a first speed and a second power signal to the first electromotor  100  for operating the first electromotor  100  at a second, lower, speed. The second power signal may be effectively lower than the first power signal, for selectively operating the first electromotor  100  at different speeds. Hence, the door control module  370  may be considered to provide a virtual transmission for the first powertrain, which is selectively operable according to at least two virtual transmission ratios. A first of the two virtual transmission ratios may be associated with the first power signal, and a second one of the two virtual transmission ratios may be associated with the second, lower, power signal. Such embodiment of the system may include the prior art adjustment device  144 , the adjustment device  44  as described herein, or another adjustment device. 
     In an embodiment, the second power signal may be a modulated power signal  7 , such as a pulse-width modulated power signal, for reducing an average power supply to the first electromotor  100 . In an embodiment, the door control module  370  is configured to reduce the power supply to the first electromotor  100 , e.g. by means of pulse width modulation or voltage reduction, only in case the frame  46 ,  48  is within a predefined angular range of positions about the first pivot axis  50 , for example if frame  46 ,  48  is close to the extended position, to reduce the adjustment speed about the first pivot axis  50  within this range of positions. Hereto, the system  400  may comprise a sensor  56  for sensing a position of the frame  46 ,  48 , particularly of a position of the first frame part  46  relative to the base  74  and/or the first frame part  46  relative to the second frame part  48 . In an embodiment, the sensor  56  comprises a potentiometer or ripple counter, for determining a position of the frame  46 ,  48  relative to the base  74 . The door control module  370  may be connected to the sensor  56 , and configured to receive a sensor signal from the sensor  56  indicative of the position of the frame  46 ,  48 . The door control module  370  may be configured to modulate the received power signal, and send the modulated power signal to the first electromotor  100 , for example, based on the received sensor signal. 
     In an embodiment, the system comprises an intermediate control unit  380  interconnected between the door control module  370  and the first electromotor  100  and/or the second electromotor  200 , as exemplified in  FIG.  5 B . The intermediate control unit may be considered part of the external vision unit  300 . It may for example be accommodated within the cavity  360  formed by the shell-shaped cover  350 . In an embodiment, the intermediate control unit  380  is configured to modulate a power signal  5  from the door control module  370  to the first electromotor  100  and/or the second electromotor  200 . For example, the intermediate control unit  380  may be configured to receive a power signal  5  from the door control module  380 , and, based on the received power signal  5 , send a modulated power signal  7  to the first electromotor  100 . In an embodiment, the modulated signal  7  may have a lower power than the received power signal  5 . For example, the intermediate control unit  380  may reduce a voltage of the power signal  5  received from the door control module. In an embodiment, the modulated signal is a pulse-modulated signal, such as a pulse-width-modulated signal. 
     In an embodiment, the intermediate control unit  380  is configured to send the modulated power signal  7  to the first electromotor  100 , further based on a position of the frame  46 ,  48 , for example a position of the first frame part  46  relative to the base  74  and/or relative to the second frame part  48 . In an embodiment, the intermediate control unit  380  may be configured to only reduce the power supply to the first electromotor  100  in case the frame  46 ,  48  is within a predefined angular range of positions about the first pivot axis  50 , for example close to the extended position, to reduce the adjustment speed about the first pivot axis  50  within this range of positions. Hereto, the system  400  may comprise a sensor  56  for sensing a position of the frame  46 ,  48 . In an embodiment, the system  400  may comprise a sensor  56  for sensing a position of the first frame part  46  relative to the base  74  and/or the first frame part  46  relative to the second frame part  48 . The intermediate control unit  380  may be connected to the sensor  56 , and configured to receive a sensor signal from the sensor  56  indicative of the position of the frame  46 ,  48 . The intermediate control unit  380  may be configured to modulate the received power signal  5 , and send the modulated power signal  7  to the first electromotor  100 , based on the received sensor signal  5 . 
     Herein, the invention is described with reference to specific examples of embodiments of the invention. One of ordinary skill in the art will appreciate that various modifications and changes may be made therein, without departing from the essence of the invention. For the purpose of clarity and a concise description, features are described herein as part of the same or separate embodiments; however, alternative embodiments having combinations of all or some of the features described in these separate embodiments are also envisaged. 
     Other modifications, variations, and alternatives are also possible. The specifications, drawings and examples are, accordingly, to be regarded in an illustrative sense rather than in a restrictive sense. 
     For the purpose of clarity and a concise description, features are described herein as part of the same or separate embodiments; however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described. 
     In the claims, the word “comprising” does not exclude the presence of other features or steps not listed in a claim. Furthermore, the words ‘a’ and ‘an’ shall not be construed as limited to ‘only one’, but instead are used to mean ‘at least one’, and do not exclude a plurality. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to an advantage.