Construction equipment with an advanced hybrid power supply

Abstract

Remote-controlled construction equipment (100) comprising a hybrid electrical power system (110), the hybrid electrical power system (110) comprising a control unit (120), an external power interface (130) arranged to be connected to an external electrical power source (180), and an on-board auxiliary power source (140), where the external power interface (130) and the auxiliary power source (140) are interconnected by a direct current, DC, bus (230), to jointly power one or more actuators (240) on the construction equipment (100), where the external power interface (130) is connected to the DC bus (230) via a rectifier (210), where the on-board auxiliary power source (140) is directly connected to the DC bus (230) in use.

Description

[0001] TITLE

[0002] CONSTRUCTION EQUIPMENT WITH AN ADVANCED HYBRID POWER SUPPLY

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to electrically powered construction equipment and to electrically powered tracked demolition robots in particular. There are disclosed construction equipment, remote-controlled demolition robots, as well as methods and control units for controlling electrically powered construction equipment.

[0005] BACKGROUND

[0006] Demolition robots are relatively light-weight and agile construction equipment which can be used for various work tasks, such as smaller excavation jobs, transportation of materials at a work site, and of course demolition.

[0007] Demolition robots and other types of heavy-duty construction equipment are often electrically powered via cable from electrical mains at the work site. This power supply may not always be dependable, i.e., may not always be capable of providing stable and sufficient power for completion of a work task at the site. An under-rated and / or unstable power supply may complicate the work task and cause unwanted interruptions.

[0008] An electrical mains connection may not always be available, such as when transporting construction equipment to a work site.

[0009] Hybrid demolition robots comprise an auxiliary power source, such as a battery, which can be used as complement to an insufficient electrical mains connection or as a temporary alternative to electrical mains power, thereby allowing the demolition robot to operate at work sites with under-rated electrical mains.

[0010] EP2842213B1 describes an example demolition robot which comprises a hybrid power system.

[0011] There is a need for improvements in the design of electrically powered construction equipment, and in particular electrically powered tracked demolition robots. SUMMARY

[0012] It is an objective of the present disclosure to provide improved hybrid electrical systems for demolition robots and other types of construction equipment. This objective is at least in part obtained by remote-controlled construction equipment according to the appended claims.

[0013] Aspects of the present disclosure relate to construction equipment such as a remote- controlled demolition robot comprising a hybrid electrical power system. The power system comprises a control unit, an external power interface arranged to be connected to an external electrical power source, and an on-board auxiliary power source such as a battery system. The external power interface and the auxiliary power source are interconnected to jointly power one or more actuators on the construction equipment. The control unit is configured to control discharge of the auxiliary power source in dependence of a state of charge (SOC) of the auxiliary power source. This way the operation of the hybrid system is improved, and faults may be avoided. Improved operation is, in particular, obtained when the auxiliary power source is close to depletion, i.e., has a low SOC.

[0014] The control unit is optionally configured to control charging and / or discharging of the auxiliary power source in dependence of a temperature of the auxiliary power source. This way damage to the auxiliary power source can be avoided.

[0015] The auxiliary power source may also comprise a combination of electrical energy storage devices, such as a battery pack and a capacitor arrangement. In this case the control unit can be configured to control charging and / or discharging of the battery pack and the capacitor arrangement jointly in dependence of a state of the construction equipment. The capacitor arrangement can for instance be used to provide high power while the battery pack can be used to store a larger amount of energy.

[0016] The present teachings are applicable both to alternating current (AC) bus structures and to direct current (DC) bus structures.

[0017] According to a preferred embodiment, the auxiliary power source is interconnected with the external power interface via a boost converter circuit or Joule thief circuit that is configured to increase a voltage of the auxiliary power source in case the SOC fails to meet a first SOC acceptance criterion. The boost converter allows the auxiliary energy source to remain connected and contribute to powering the different actuators on the construction equipment even as it is approaching depletion, which is an advantage.

[0018] According to some aspects, the control unit is arranged to control a hydraulic oil flow in a hydraulic circuit of the construction equipment in dependence of a hydraulic pressure in the hydraulic circuit and a maximum total power outtake of the external electrical power source and the on-board auxiliary power source. This means that the control unit balances the power outtake given by the product of hydraulic pressure and flow against the total available power, such that operation can be maintained with small impact on usability, despite challenges with the total available power to the hybrid energy system. The control unit will automatically respond to an increased hydraulic pressure in the system by lowering hydraulic flow if the total available power is not enough to support the increased power outtake from the hybrid electrical power system.

[0019] The auxiliary power source can optionally be interconnected with the external power interface via a battery protection circuit that is configured to disconnect the auxiliary power source from the one or more actuators in case the SOC fails to meet a second SOC acceptance criterion. This way the auxiliary energy source is protected from damage as it nears depletion, which is an advantage.

[0020] The control unit can also be configured to initiate generation of a notification message to a display unit of a remote control device in case the SOC fails to meet a third SOC acceptance criterion. This way the operator of the construction equipment becomes aware of the SOC-situation and can potentially take action to improve the situation.

[0021] According to some aspects, the control unit is arranged to control charging of the auxiliary power source based on a present power consumption of the one or more actuators on the construction equipment. This way the control unit can balance the charging current to the auxiliary energy source against the power need of the actuators, so as to not exceed the total available power from the external power source. The auxiliary energy source charging current then goes up when the power requirements of the actuators on the construction equipment is low, and vice versa, which increases the useability of the construction equipment at work sites with underrated external power sources.

[0022] The hybrid electrical power system optionally comprises a power sensor that is arranged to monitor frequency and / or voltage characteristics of an AC over the external power interface. In this case the control unit is arranged to detect a time variation in frequency and / or voltage of the AC based on an output signal from the power sensor and trigger one or more automated actions in response to detecting a time variation in frequency and / or voltage which fails to meet a power stability criterion. This allows the system to adapt to unstable external power sources, which is an advantage. The system can, for instance, reduce a load on the external power source if it is detected that this external power source is nearing its limit for delivering stable power. The one or more automated actions may, for instance, comprise a regulation of charging power of the auxiliary power source, and / or an adjustment of hydraulic flow delivered by a hydraulic pump comprised in the one or more actuators of the construction equipment.

[0023] Aspects of the present disclosure relate to remote-controlled construction equipment, such as a remote-controlled demolition robot, with a hybrid electrical power system that comprises a control unit, an external power interface arranged to be connected to an external electrical power source such as electrical mains, and an on-board auxiliary power source such as a battery. The external power interface and the auxiliary power source are interconnected by a DC bus to jointly power one or more actuators on the construction equipment, such as an electric motor used to power a hydraulic pump. The external power interface is connected to the DC bus via a rectifier, i.e., an AC / DC module, while the on-board auxiliary power source is directly connected to the DC bus in use. Thus, there is no intermediate power electronics like switches, diodes, or DC / DC modules arranged between the on-board auxiliary power source and the power consumers connected to the DC bus. Any power drawn by the one or more actuators connected to the DC bus that is not delivered by the external power interface via the rectifier will appear as a load on the auxiliary power source. Also, any surplus electrical energy on the DC bus will result in a charging current to the auxiliary power source. This way a hybrid electrical power system of low complexity is obtained, which does not require advanced control of switches or the like. The latency in delivering electrical energy from the auxiliary energy source to the DC bus is minimized, since the auxiliary energy source is always connected to the DC bus in use. There is no need for active control of the auxiliary power source since it is always connected to the DC bus. Electrical current will pass to and from the auxiliary power source in dependence of the operations and states of the different loads connected to the DC bus, and in dependence of how much electrical power that is delivered to the DC bus by the rectifier.

[0024] The one or more actuators on the construction equipment normally comprise at least one electric motor that is connected to the DC bus via a motor driver, such as an inverter. The electric motor can be a pump motor of a hydraulic system, a drive motor for moving endless tracks or drive wheels, or some other electric motor. The motor driver consumes DC power from the DC bus and converts the DC power into alternating drive currents for the motor, i.e., time variable winding currents of the electric motor. The motor driver can be controlled independently from the hybrid electrical power system, which is an advantage. This is made possible since the auxiliary power source is always connected to the DC bus, and hence the DC bus carries electrical power at least as long as the auxiliary power source has sufficient charge. When the auxiliary power source is depleted the hybrid electrical system will be shut down, since then there is no longer sufficient power to operate the construction equipment.

[0025] The rectifier is, according to a preferred embodiment, adapted to limit a current drawn over the external power interface from the external electrical power source according to a configuration parameter of the rectifier, such as a configurable maximum current. Particular advantages are obtained if the configuration parameter comprises or is derived from a fuse type of the external electrical power source, such as a type of miniature circuit breaker (MCB) used at the work site and a rating of the fuse in terms of tripping current. The control unit and / or a remote control device of the construction equipment can for instance be arranged to obtain information associated with the fuse type of the external electrical power source from a user interface of the construction equipment and configure a power limitation function of the external power interface in accordance with the fuse type of the external electrical power source. This way the operation of the construction equipment can be matched to the electrical power available at a given work site. Some work sites may, e.g., comprise fusing systems which are sensitive to peak current, while other work sites may comprise fusing systems that are more sensitive to average current consumed over some time period. An operator desiring to use the remote-controlled construction equipment at a work site simply inputs the fuse type in use at the work site and / or the tripping current of the fuse, whereupon the remote-controlled construction equipment automatically adjusts to the electrical mains at the work site. The remote-controlled demolition robots and the construction equipment described herein optionally comprise a decommissioning switch that is arranged to disconnect the on-board auxiliary power source from the DC bus and from the rest of the hybrid electrical system of the construction equipment in a decommissioned mode of the hybrid electrical power system. The manual decommissioning switch allows the equipment to be serviced without risk of coming into contact with any hot wires (electrical conductors carrying electricity) or the like, which could otherwise pose a risk to a service technician. The construction equipment, nor the hybrid electrical system, is not in use when in the decommissioned mode. The decommissioning switch is preferably a switch which visually indicates when it is in disconnected state. The decommissioning switch is normally also lockable, meaning that only a person having the right key is able to unlock and close the switch.

[0026] The control unit optionally comprises a first part arranged to communicate with and / or control at least one of the one or more actuators on the construction equipment via a first control channel, and a second part that is separate from the first part and arranged to communicate with and / or control one or more operations of the rectifier via a second control channel. The first and the second control channels may be analog control channels, such as control voltages or currents, or digital control channels over which control messages can be exchanged, such as controller area network (CAN) channels. In other words, the control system of the equipment can be divided into one part that controls the actuators of the machine, and another part that controls the hybrid electrical power system. The control of the actuators then does not have to account for the operations of the hybrid electrical power system, and vice versa. This results in a less complicated overall control system of the construction equipment.

[0027] Aspects of the present disclosure also relate to construction equipment such as a remote-controlled demolition robot that comprises a hybrid electrical power system. The power system comprises a control unit, an external power interface arranged to be connected to an external electrical power source, and an on-board auxiliary power source. The external power interface and the auxiliary power source are interconnected to jointly power one or more actuators on the construction equipment, e.g., via a common DC bus or a common AC bus. The control unit is arranged to obtain information associated with a SOC of the auxiliary power source, and to detect when the SOC fails to meet a SOC mobility acceptance criterion. The control unit is configured to inactivate at least one work-task related actuator on the construction equipment, such as a breaker or other tool, or an actuator controlling a tool carrier arm of the construction equipment, in response to detecting that the SOC fails to meet the SOC mobility acceptance criterion. The control unit is also configured to allow activation of a transport-task related actuator on the construction equipment, such as a drive motor of endless tracks or drive wheels of the equipment, despite detecting that the SOC fails to meet the SOC mobility acceptance criterion. This way enough power for moving the equipment away from a work site can be preserved. For instance, in the event of a power outage in electrical mains, the machine will shut down operations involving tools in time to allow the remaining energy in the auxiliary power source to be used for transporting the equipment away from the work site.

[0028] Aspects of the present disclosure also relate to construction equipment such as a remote-controlled demolition robot that comprises a hybrid electrical power system. The power system comprises a control unit, an external power interface arranged to be connected to an external electrical power source, and an on-board auxiliary power source. The external power interface and the auxiliary power source are interconnected to jointly power one or more actuators on the construction equipment, e.g., via a common DC bus or a common AC bus. The control unit and / or a remote control device of the remote-controlled construction equipment is arranged to configure a power limitation function of the external power interface in accordance with the fuse type of the external electrical power source. This way operations of the remote-controlled construction equipment can be tailored or even optimized to the fuse configuration at a given work site. The remote-controlled construction equipment can be operated at a work site with under-rated fuses with a reduced risk of tripping the fuse.

[0029] Aspects of the present disclosure also relate to construction equipment such as a remote-controlled demolition robot that comprises a hybrid electrical power system. The power system comprises a control unit, an external power interface arranged to be connected to an external electrical power source, and an on-board auxiliary power source. The external power interface and the auxiliary power source are interconnected to jointly power one or more actuators on the construction equipment, e.g., via a common DC bus or a common AC bus. The hybrid electrical power system comprises a manual decommissioning switch that is arranged to disconnect the onboard auxiliary power source from the remote-controlled construction equipment in a decommissioned mode of the hybrid electrical power system. The manual decommissioning switch allows for servicing of the equipment with a reduced risk of electrical shocks and a reduced risk of other damage incurred by the auxiliary energy source.

[0030] There are also disclosed methods and various forms of construction equipment associated with the same advantages as discussed above in connection to the control units.

[0031] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

[0032] BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present disclosure will now be described in more detail with reference to the appended drawings, where:

[0034] Figure 1 illustrates an example demolition robot;

[0035] Figures 2A-B schematically illustrate example hybrid electrical energy systems;

[0036] Figures 3A-B show additional example hybrid electrical energy systems;

[0037] Figures 4A-D schematically illustrate example actuator structures;

[0038] Figure 5 shows an example remote control device;

[0039] Figure 6 is a flow chart illustrating methods;

[0040] Figure 7 schematically illustrates a control unit; and

[0041] Figure 8 schematically illustrates a computer program product; DETAILED DESCRIPTION

[0042] Aspects of the present disclosure will now be described more fully with reference to the accompanying drawings. The different devices and methods disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0043] The terminology used herein is for describing aspects of the disclosure only and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0044] The technical features and functions described herein are mainly exemplified using a remote-controlled demolition robot. It is however appreciated that the technical features and functions are more generally applicable also in other type of construction equipment.

[0045] Figure 1 illustrates an example demolition robot 100. A demolition robot is a lightweight construction machine which can be used for various work tasks, such as smaller demolition tasks at a work site. A demolition robot is often tracked, i.e., the machine comprises endless tracks 150 or belts, for support on the ground surface and for propulsion as well as for maneuvering. This demolition robot 100 also comprises a rotatable tower 160 and a tool carrier arm 170, in this case a three- segmented tool carrier arm.

[0046] The tool carrier arm 170 is arranged to support a variety of different tools at its distal end, such as a breaker tool, a bucket tool, a grapple, and steel shears. Some of these tools may be actively powered tools, such as the breaker, while other tools are passive tools, such as the bucket. The active tools are normally powered by the hydraulic system of the demolition robot.

[0047] The demolition robot 100 comprises an electrical power system 110 with a control unit 120 that controls the general operation of the machine in response to, e.g., user input signals provided by an operator of the machine. A demolition robot 100 is normally remote controlled by an operator walking next to the machine and holding a remote control device 500. However, the operator and the remote control device 500 can also be located further away from the machine, such as a remote location many kilometers away. The control unit 120 is connected to the remote control device 500 by a wired or a wireless radio communication link. An example remote control device 500 will be discussed in more detail below in connection to Figure 5.

[0048] A tool such as a breaker, bucket, or steel shears may be supported on the distal end of the tool carrier arm 170 and used for various work tasks. The equipment 100 is often hydraulically powered, which means that an electric motor drives a hydraulic pump that in turn provides power to the different hydraulic actuators on the equipment in a known manner. The present disclosure is not limited to any particular form of hydraulic system. The techniques described herein are applicable with both fixed displacement pumps and variable displacements pumps. Any direct current (DC) or alternating current (AC) motor can be used to drive the hydraulic pump. A wide variety of different types of electrical motors are known in the art and will therefore not be discussed in more detail herein.

[0049] The demolition robot 100 is electrically powered via an external power interface 130, here illustrated as a cable connection, which is arranged to be connected to an external electrical power source 180 that is only schematically illustrated in Figure 1.

[0050] The external electrical power source 180 is often electrical mains, but can also be a generator, such as an internal combustion engine (ICE) powered or fuel-cell powered generator, which provides AC to the external power interface 130. The power interface 130 is normally a three-phase AC power interface. Generators are sometimes also referred to as gensets and may comprise buffer electrical energy storage systems, i.e., battery packs. Generators and gensets are generally known and will therefore not be discussed in more detail herein. It is understood that the external electrical power source 180 is physically separated from the demolition robot and connected to the demolition robot via cable.

[0051] The demolition robot also comprises an on-board electrical energy storage system which can be used to at least temporarily power one or more actuators on the demolition robot, e.g., in the event of power outage at the external power source 180, or in case of instability in the AC supply from the external power source, as will be discussed in more detail in the following. This on-board electrical energy storage system will be referred to herein as an auxiliary power source 140 and it normally comprises one or more rechargeable electrical batteries adapted to receive DC during charging and to output DC to a load during discharging. The auxiliary energy source 140 may be referred to as a electrical DC auxiliary energy source. Thus, to summarize, Figure 1 shows an example of tracked remote-controlled construction equipment 100 which comprises a hybrid electrical power system 110 with a control unit 120, an external power interface 130 arranged to be connected to an external electrical power source 180, and an on-board auxiliary power source 140. The external power interface 130 and the auxiliary power source 140 are interconnected to jointly power one or more actuators on the construction equipment 100.

[0052] Sometimes the electrical mains or genset at a work site is under-rated, i.e., not dimensioned to provide the necessary power to the demolition robot 100 when it operates at peak power, e.g., when a high power breaker is active. Some demolition robots may, e.g., require a 64A or a 32A electrical mains connection, which may not be supported at all work sites. To improve the situation with under-rated external power sources at work sites, the demolition robot 100 may draw power from the onboard auxiliary power source 140 in order to complement the external electrical power source 180. The auxiliary power source 140 normally comprises one or more batteries, but may also comprise super-capacitors, on-board fuel cell systems, onboard gensets, or other electrical energy sources. The auxiliary power source 140 can also be used to at least temporarily power mobility actuators of the equipment 100, such as the tracks 150 or driven wheels of the equipment (not shown in Figure 1 ).

[0053] Electrically powered construction equipment is often powered via long cables which may cause voltage drops due to insufficient wire gauge (cross-section area of the cable), especially if high power electrical load is applied at the interface 130. Frequency variation in the AC over the power interface 130 may also be experienced at some work sites, in particular work sites where an ICE generator is used as electrical power source 180. This is because most generators take some time to increase the power production in response to a rapid change in load at the interface 130. The ICE of a generator may, e.g., lose rotation speed in response to the increase in torque at the motor axle. This reduction in motor axle speed may in some cases translate directly into a reduction in frequency of the AC output.

[0054] A too large drop in voltage over the interface 130 may cause problems in, e.g., electrical motors on the demolition robot 100, such as hydraulic pump motors and other actuator motors, which may experience an increased thermal load due to the increased motor currents that result from a drop in voltage. This increase in thermal load may not be overly problematic as it only occurs during a limited duration of time but can cause large irreparable damage if persistent. The on-board auxiliary power source 140 can be used to mitigate the consequences of power drop due to long cables, by adding additional power to bring the voltage back up to the specified level.

[0055] A decrease or drop in AC frequency over the interface 130 in response to an increase in electrical load on the interface is often indicative of that an ICE generator is used to power the demolition robot, and that this generator is overloaded, i.e., that the generator is too small to provide sufficient power. A generator that is overloaded may shut down, or even suffer damage due to the overload, which of course is undesired. A malfunctioning generator will cause undesired interruption in the work task performed by the demolition robot 100. The on-board auxiliary power source 140 can be used to mitigate the consequences of this type of frequency instability by adding power to reduce the load on the generator.

[0056] The demolition robot 100 is sometimes connected via wireless link to a remote server 190. This remote server may be comprised in a back-end system associated with the demolition robot. The back-end system may provide functions such as performance monitoring, over-the-air updating of control unit software, service, and maintenance functions, and so on. The remote server may store one or more configuration parameters for the demolition robot 100, and in particular configuration settings related to the operations of the hybrid electrical power system of the demolition robot 100. These settings may, e.g., relate to tripping characteristics of different fusing systems, various settings of rectifiers and other components of the hybrid electrical power systems, and so on. Fuse tripping characteristics will be discussed in more detail below.

[0057] A demolition robot is an example of remote-controlled construction equipment, i.e., equipment where an operator controls the equipment from a location separated from the equipment, as opposed to from a control seat or cabin mounted on the construction equipment. Other examples of remote-controlled construction equipment comprises remote-controlled floor saws, remote-controlled power trowels, remote- controlled floor grinders, remote-controlled floor-polishing machines, and the like. The hybrid electric power systems described herein are generally applicable in remote- controlled construction equipment. Particular advantages are obtained when the hybrid electrical power systems are used in remote-controlled demolition robots since these machines are often used at work sites with unstable and / or under-rated electrical mains. Remote-controlled demolition robots and other types of remote- controlled construction equipment often need to be transported between sites where electrical mains is available. At least some of the hybrid electrical power systems described herein allow more efficient transport in absence of a fully functional electrical main connection.

[0058] Figure 2A schematically illustrates a power system 110 that is based on a direct current (DC) bus architecture. The power system 110 in Figure 2A comprises a rectifier or AC / DC module 210 which transforms AC from the external power interface 130 into DC that is fed onto the DC bus 230. One or more actuators 240 draw DC power from the DC bus. To complement the power drawn via the external power interface 130, an auxiliary power source 140 is connected to the same DC bus 230 via a DC / DC module 220. The control unit 220 controls both the AC / DC module 210 and the DC / DC module 220. The auxiliary energy source may provide electrical power to the DC bus during a discharge operation of the auxiliary energy source 140, and most auxiliary energy sources, such as batteries, can also be charged from the DC bus. The control unit 220 controls the magnitude of the discharge current from the auxiliary power source 140 and also the magnitude of the charge current to the auxiliary energy source 140.

[0059] Figure 3A and 3B show example hybrid electrical power systems 110 where the auxiliary power source 140 (here indicated as a battery) is instead directly connected to the DC bus 230, i.e., without, e.g., an intermediate DC / DC module 220 arranged inbetween the auxiliary power source 140 and the DC bus 230. Here “directly connected to the DC bus” means that no frequency conversion, nor any voltage conversion occurs between the auxiliary power source 140 and the DC bus 230. A direct connection between the auxiliary power source 140 and the DC bus 230 may comprise a decommissioning switch which is always closed in use. A direct connection between the auxiliary power source 140 and the DC bus 230 may also comprise a passive component such as a resistance or the like, as long as no active frequency or voltage conversion takes place between the auxiliary power source 140 and the DC bus 230. A direct connection between the auxiliary power source 140 and the DC bus 230 excludes a diode function which prevents current from flowing from the DC bus 230 to the auxiliary energy source 140.

[0060] Figure 2B shows a similar power system 110, but this system is instead based on an AC bus architecture. The external power interface 130 is connected to the AC bus 270 via an AC / AC module 250 and the auxiliary power source 140 is connected to the same AC bus 270 via a DC / AC module 260. One or more actuators 280 draw power from the AC bus, either directly as AC or via rectifiers that transform AC from the AC bus into DC for powering the actuator. Figures 4A-D illustrate some example actuators 240, 280 which draw power from either a DC bus as in Figures 4A-B or from an AC bus as in Figures 4C-D. These actuators comprise electrical motors arranged to drive hydraulic pumps in a known manner.

[0061] In Figure 4A, an inverter or DC / AC module 410 converts DC power from the DC bus 230 into AC to power an AC motor 415 which is connected to a hydraulic pump 420.

[0062] In Figure 4B, a DC / DC module 430 converts DC power from the DC bus 230 into DC to power a DC motor 435 which is connected to a hydraulic pump 420.

[0063] In Figure 4C, an AC / AC module 450 converts AC power from the AC bus 270 into AC to power an AC motor 455 which is connected to a hydraulic pump 460.

[0064] In Figure 4D, an AC / DC module 470 converts AC power from the AC bus 270 into DC to power a DC motor 475 which is connected to a hydraulic pump 460.

[0065] It is important that the auxiliary power source 140 is used as complement to the external power interface 130 in a controlled manner, and not overloaded since otherwise the auxiliary power source may be damaged or subject to unnecessary wear. To improve handling of the auxiliary power source 140, the control unit 120 is configured to control discharge of the auxiliary power source 140 in dependence of a state of charge (SOC) of the auxiliary power source 140, and not try to draw more power from the auxiliary power source 140 than it is capable of providing in a stable manner.

[0066] The auxiliary power source optionally comprises one or more temperature sensors, and the control unit is optionally configured to control charging and / or discharging of the auxiliary power source in dependence of a temperature of the auxiliary power source. The charging and / or discharging current is limited as function of temperature. There is normally a temperature window associated with a battery pack, and the charging and discharging current is preferably limited in case the battery is too cold or too hot. This way damage to the auxiliary power source can be avoided.

[0067] According to a preferred embodiment, the auxiliary power source 140 is interconnected with the external power interface 130 via a boost converter circuit or Joule thief circuit configured to increase a voltage of the auxiliary power source 140 in case the SOC fails to meet a first SOC acceptance criterion. This is beneficial if the auxiliary power source starts to drop in voltage, since the boost converter circuit can compensate for the voltage drop at the auxiliary power source and draw out additional energy remaining in the auxiliary power source. The first SOC acceptance criterion may be a predetermined voltage threshold that has been configured after practical experiments and / or mathematical analysis of the hybrid power system operations.

[0068] A boost converter or step-up converter is, generally, a DC / DC module that increases voltage, while decreasing current, from its input (supply) to its output (load). According to an example, it is a class of switched-mode power supply (SMPS) containing at least two semiconductors, a diode, and a transistor, and at least one energy storage element: a capacitor, inductor, or the two in combination. To reduce voltage ripple, filters made of capacitors (sometimes in combination with inductors) are normally added to such a converter's output (load-side filter) and input (supply-side filter). Boost circuits of this kind are generally known and will therefore not be discussed in more detail below.

[0069] An unregulated boost converter is used as the voltage increase mechanism in the example boost converter circuit known as the "Joule thief". This design is commonly based on blocking oscillator concepts, although other realizations are also possible. This boost converter circuit "steals" the remaining energy in a battery, even though its voltage level has dropped significantly due to depletion. The energy harvested in this manner would otherwise be wasted since the low voltage of a nearly depleted battery often makes it unusable for a normal load.

[0070] The auxiliary power source 140 may also be interconnected with the external power interface 130 via a battery protection circuit configured to disconnect the auxiliary power source 140 from the one or more actuators 240, 280 in case the SOC fails to meet a second SOC acceptance criterion. The second SOC acceptance criterion is normally specified by the manufacturer of the auxiliary power source, e.g., the battery manufacturer.

[0071] Turning now to Figure 3A and Figure 3B which illustrate examples 300, 301 of hybrid electrical power systems 1 10 that can be used with remote-controlled construction equipment such as the demolition robot 100 illustrated in Figure 1. The hybrid electrical power systems 110 comprise a control unit 120, an external power interface 130 arranged to be connected to an external electrical power source 180, and an onboard auxiliary power source 140, as discussed above. The external power interface 130 and the auxiliary power source 140 are here interconnected by a DC bus 230 to jointly power one or more actuators 240 on the construction equipment 100. The DC bus is a continuous electrical conductor which connects DC power sources to DC power consumers.

[0072] In the examples 300, 301 , the actuator 240 comprises an electric motor 320 that is powered via a motor driver 310. The motor driver 310 generally comprises power electronics adapted to convert a DC voltage into winding currents to operate the electric motor 320. The motor driver may also be referred to as an inverter. The motor driver 310 is in these examples controlled by the control unit 120 via a first control channel 121 .

[0073] The external power interface 130 is connected to the DC bus 230 via a rectifier 210, i.e., an AC / DC module, which converts alternating current from, e.g., electrical mains, to DC. In the examples 300, 301 , the on-board auxiliary power source 140 is directly connected to the DC bus 230 in use. When the construction equipment 100 is in use, whether it is being transported from one place to another or used for a work task such as operating a breaker or moving a bucket, the on-board auxiliary power source 140 is directly connected to the DC bus 230. This means that electrical current will flow from the on-board auxiliary power source 140 to the DC bus 230 and onwards to, e.g., the motor driver 310 when the motor driver consumes power above the power that is delivered by the rectifier 210. This also means that electrical current will flow from the DC bus 230 to the on-board auxiliary power source 140 (as a charging current) when the voltage at the DC bus exceeds the pole voltage of the on-board auxiliary power source 140.

[0074] A technical advantage of the direct connection between the on-board auxiliary power source 140 and the DC bus 230 is, of course, that a DC / DC module such as the DC / DC module 220 in Figure 2A is not needed. Voltage conversion by a DC / DC module always results in some losses, and the DC / DC module 220 also drives cost of the overall hybrid electrical system 110.

[0075] The rectifier 210 can be adapted to regulate a voltage on the DC bus 230 as a voltage selected from a number of discrete voltage steps. Alternatively, the rectifier 210 can be adapted to regulate the voltage on the DC bus 230 as a continuous voltage over a predetermined voltage range from a minimum voltage to a maximum voltage.

[0076] A technical advantage of the direct connection between the on-board auxiliary power source 140 and the DC bus 230 is to simplify control of the overall operation of the hybrid electrical system 1 10. The on-board auxiliary power source 140 will always be connected to the DC bus 230, and the DC bus 230 will therefore always carry electrical power, regardless of the state of the external electrical power source 180 and the rectifier 210. For instance, if the rectifier malfunctions 210, or if the control functionality of the hybrid electrical system 110 malfunctions, there will still be DC voltage on the DC bus 230 to, e.g., allow transport of the equipment over a limited distance.

[0077] Herein, according to some aspects, a direct connection between the on-board auxiliary power source 140 and the DC bus 230 means that there is a direct electrical connection via a continuous electrical conductor between the on-board auxiliary power source 140 and the at least one power consumer, such as the motor driver 310 or other electrical power consumer connected to the DC bus 230.

[0078] According to a preferred embodiment, the rectifier 210 is adapted to limit a current drawn over the external power interface 130 from the external electrical power source 180 according to a configuration parameter of the rectifier 210. The configuration parameter of the rectifier 210 need not necessarily be stored in the rectifier 210, it can also be stored, e.g., by the control unit 120 which controls the operations of the rectifier 210. The configuration parameter of the rectifier 210 may comprise a maximum current to be drawn over the external power interface 130 or a maximum power. The maximum current or power to be drawn over the external power interface 130 may be associated with different time windows, such as time windows matched to tripping characteristics of a given fuse type, such as a miniature circuit breaker (MCB) type. An MCB is an electrical device that automatically switches off an electrical connection to an electrical circuit during an abnormal condition.

[0079] Type A MCBs are designed to provide protection against over-current. They are suitable for use in circuits where the maximum expected current is known and relatively constant, such as lighting circuits.

[0080] Type B MCBs are designed to provide protection against over-current and short circuits. They are suitable for use in circuits where the load is variable, such as in motor circuits.

[0081] Type C MCBs are designed to provide protection against both over-current and earth fault currents. They are suitable for use in circuits where there is a high risk of earth fault currents, such as in circuits powered by DC or in circuits that include sensitive electronic equipment. Type D MCBs are designed to provide protection against over-current and earth fault currents, with a higher tripping threshold than Type C MCBs. They are suitable for use in circuits where there is a high risk of earth fault currents, but where the fault current is expected to be higher than what can be protected by Type C MCBs.

[0082] Type G MCBs are designed to provide protection against over-current and earth fault currents in residual current devices (RCDs) used in electrical systems.

[0083] Type H MCBs are designed to provide protection against over-current and earth fault currents in electrical systems that are powered by DC.

[0084] Type K MCBs are designed to provide protection against over-current and short circuits in electrical systems with high fault levels.

[0085] The relationship between current and time with regards to tripping of a fuse is normally referred to the tripping characteristics of the fuse.

[0086] There is disclosed herein a remote-controlled demolition robot 100 comprising a hybrid electrical power system 110, 300 and a remote control device 500. The power system 110, 300 comprises a control unit 120, an external power interface 130 arranged to be connected to an external electrical power source 180, and an on-board auxiliary power source 140. The external power interface 130 and the auxiliary power source 140 are interconnected to jointly power one or more actuators 240, 280 on the construction equipment 100. The control unit 120 and / or the remote control device 500 which will be discussed in more detail below in connection to Figure 5, is / are arranged to obtain information associated with a fuse type of the external electrical power source 180. The control unit 120 and / or the remote control device 500 is / are also arranged to configure a power limitation function of the external power interface 130 in accordance with the fuse type of the external electrical power source 180.

[0087] By configuring the power limitation function of the external power interface 130 in accordance with the fuse type of the external electrical power source 180, the hybrid electrical power system 1 10, 300 will only draw an amount of power that can be supported by the external electrical power source 180, and not more. This means that the hybrid electrical power system 110, 300 can remain operational even when the external electrical power source 180 has a fuse type with a current rating below a maximum current consumption of the one or more actuators 240, 280.

[0088] The fuse type may, e.g., be selectable by an operator via the remote control device of the construction equipment 100, or via an interface on the construction equipment 100. Example fuse types may, e.g., comprise legacy porcelain fuses and MCBs of different current ratings, such as 10A, 16A, 32A, 64A. The number of phases of the external electrical power source 180, and their respective current or power ratings can also be a selectable fuse type.

[0089] The remote-controlled demolition robot 100 may, according to some aspects, also comprise a manual decommissioning switch 340 arranged to physically disconnect the on-board auxiliary power source 140 from the remote-controlled demolition robot 100, such as from the DC bus 230, in a decommissioned mode of the hybrid electrical power system 110. This manual decommissioning switch can be used when servicing the remote-controlled demolition robot 100, e.g., at a work-shop. The manual decommissioning switch 340 is not inextricably linked to any other aspects of the hybrid electrical power systems or construction equipment discussed herein. The manual decommissioning switch physically separates the on-board auxiliary power source 140 from the rest of the system, such that a service technician does not risk coming into contact with any hot wires or the like, which could present a hazard during servicing of the remote-controlled demolition robot 100. The manual decommissioning switch is preferably a lockable switch that requires a physical key or digital code in order to unlock. The manual decommissioning switch preferably comprises a visual indication that clearly shows when the manual decommissioning switch is open (where the on-board auxiliary power source 140 is electrically separated from the rest of the system) and when the manual decommissioning switch is closed (where the on-board auxiliary power source 140 is electrically connected to the rest of the system).

[0090] Figure 3B shows an example 301 where the control unit 120 comprises a first part 350 (indicated as control circuit 1 ) arranged to communicate with and / or control at least one of the one or more actuators 240 on the construction equipment 100 via a first control channel 121. The first part 350 of the control unit 120 may be physically separated from one or more other parts of the control unit 120, such as from a second part 360 of the control unit 120. The first part 350 of the control unit 120 may also be integrated with the one or more other parts, such as on the same printed circuit board (PCB).

[0091] The first part 350 of the control unit 120 here control the motor driver 310. The control of the one or more actuators 240 on the construction equipment 100 may be performed by the first part 350 of the control unit 120 separately from control of the transfer of electrical power to and from the DC bus 230. This means that control of the actuators can be implemented independently of the different power functions on the demolition robot 100. The motor driver thus operates in the same manner regardless of the status of the power supply, i.e., if the power is coming from the onboard auxiliary power source 140 and / or from the external electrical power source 180. This is an advantage since the actuator control is simplified. The first part 350 of the control unit 120 may be configured to control the one or more actuators based on control input signals received from a movement control system 380 of the demolition robot 100, as schematically illustrated in Figure 3B. The movement control system 380 may form part of the remote control device 500 that will be discussed in more detail below in connection to Figure 5.

[0092] According to some aspects, the control unit 120 comprises a second part 360 (indicated in Figure 3B as control circuit 2). The second part 360 is arranged to communicate with and / or control one or more operations of the rectifier 210 and / or the on-board auxiliary power source 140 via a second control channel 122. Consequently, the control of the hybrid electrical power system 110 is performed by the second part of the control unit 120, which may be separate from the first part that handles control of the actuators. This results in a simplification of the overall control of the remote-controlled demolition robot 100, which is an advantage.

[0093] The second part 360 of the control unit 120 is optionally arranged to display 390 a status message associated with a status of the hybrid electrical power system 1 10 on a display device of the construction equipment 100, such as on a display of the remote control device 500 or on a display mounted on the demolition robot.

[0094] The hybrid electrical power system 1 10 optionally comprises a battery management system (BMS) 330 arranged to communicate with and / or control one or more operations of the rectifier 210 and / or the on-board auxiliary power source 140.

[0095] A BMS 330 is, generally, designed to promote safety, efficiency, and longevity of batteries. The primary purpose of a BMS is to monitor and regulate the battery’s operation, protecting it from conditions that could reduce its lifespan or create hazards. Some example key Functions of a BMS may comprise;

[0096] Monitoring: A BMS may continuously track key battery parameters, such as voltage, current, temperature, and SOC. It may therefore ensure that each cell within a battery pack remains within safe operating limits. Balancing: In multi-cell battery packs, cells can discharge at different rates, leading to imbalances. A BMS may actively balance the cells, redistributing energy as necessary to maintain uniform charge levels, thereby enhancing the pack's overall performance and capacity.

[0097] Protection: The BMS may also safeguard against risks such as overcharging, overdischarging, and overheating. It can prevent damage to the battery by disconnecting it from the load or charger under hazardous conditions.

[0098] Estimating State of Health (SOH): By analyzing factors like capacity fade and resistance increase over time, a BMS can predict a battery’s remaining useful life, aiding in maintenance planning and reducing unexpected failures.

[0099] Communication and Diagnostics: Some BMSs feature communication interfaces that allow them to share data with external systems or user interfaces. This enables remote diagnostics, real-time monitoring, and optimization of battery usage in applications like electric vehicles and grid storage.

[0100] Construction equipment like remote controlled demolition robots are heavy and difficult to move around if the transportation actuators on the equipment, such as the tracks 150 are rendered inoperable. One major advantage of the hybrid electrical power systems 110 discussed herein is that they allow the equipment 100 to be moved around even if there is no external electrical power source 180 available for powering the equipment. However, the machine will still be rendered immobile if the on-board auxiliary power source 140 is fully depleted.

[0101] It has been realized that the hybrid electrical power systems 110 discussed herein can be configured with a mobility function that ensures that the construction equipment 100 can always be transported in the event of electrical energy shortage. This function comprises monitoring a current SOC of the on-board auxiliary power source 140 and comparing the SOC to a mobility acceptance criterion. The mobility acceptance criterion may, e.g., be a threshold set at around 20% of full charge which ensures that there is always enough power remaining to move the equipment away from a work and, e.g., to a transport vehicle such as a trailer or the like, or to a charging station where the on-board auxiliary power source 140 can be recharged to a higher SOC. The SOC mobility acceptance criterion may also comprise a requirement on estimated remaining operating time, estimated transportation distance capability, or the like. In case the SOC of the on-board auxiliary power source 140 fails to meet the SOC mobility acceptance criterion, then all actuators except for the mobility actuators can be inactivated in order to conserve the remaining power for moving the equipment away from the work site. The SOC mobility acceptance criterion may be configurable by an operator. An operator may, for instance, input a minimum transportation distance which ensures that the equipment can always be transported back to some location, in the event of a power outage in electrical mains.

[0102] To summarize, the present disclosure relates to a remote-controlled demolition robot 100 comprising a hybrid electrical power system 1 10, 300. The power system 110, 300 comprises a control unit 120, an external power interface 130 arranged to be connected to an external electrical power source 180, and an on-board auxiliary power source 140. The external power interface 130 and the auxiliary power source 140 are interconnected to jointly power one or more actuators 240, 280 on the construction equipment 100. The control unit 120 is arranged to obtain information associated with a SOC of the auxiliary power source 140 and detect when the SOC fails to meet a SOC mobility acceptance criterion, such as a reconfigurable or fixed SOC threshold, a requirement on estimated remaining operating time, and / or a requirement on estimated remaining energy amount. The control unit 120 is configured to inactivate at least one work-task related actuator 240, 280 on the construction equipment 100 in response to detecting that the SOC fails to meet the SOC mobility acceptance criterion, while allowing activation of a transport-task related actuator on the construction equipment 100 despite detecting that the SOC fails to meet the SOC mobility acceptance criterion. In other words, when the SOC of the onboard auxiliary power source 140 fails to meet the SOC mobility acceptance criterion, then all functions on the equipment are disabled except for the functions related to transportation of the equipment, such as propulsion of the endless tracks and perhaps also tower rotation and some rudimentary tool carrier arm movements. A high power tool such as a breaker or the like will be inactivated when the SOC of the on-board auxiliary power source 140 fails to meet the SOC mobility acceptance criterion.

[0103] Figure 5 shows an example remote control device 500 with a display unit 510 and joysticks 520. The control unit 120 is preferably configured to initiate generation of a notification message to the display unit 510 of the remote control device 500 in case the SOC fails to meet a third SOC acceptance criterion. This third acceptance criterion may be preconfigured by the control unit. It can be realized as a straightforward threshold value, or it can comprise more advanced detection criteria, including time periods and various filtering mechanisms. By displaying this information on the display unit 510, the operator becomes aware of the critically low energy level in the auxiliary power source. The operator may then take a break and let the hybrid power system recharge the auxiliary power source, such that peak power can once more be delivered by the hybrid electrical power system 110.

[0104] The control unit 120 can also be arranged to control charging of the auxiliary power source 140 based on a present power consumption of the one or more actuators 240, 280 on the construction equipment 100, i.e., in dependence of how much power the other power consumers of the demolition robot are consuming. This means that the control unit monitors actions by the demolition robot, e.g., by monitoring control input commands from an operator, hydraulic valve operations, or by measuring power consumption of the different actuators. The control unit then balances the charge current delivered to the auxiliary power source based on the present power consumption of the one or more actuators 240, 280 on the construction equipment 100, such that the overall power consumption of the hybrid power system 110 does not exceeds the total available power from the external power source 180.

[0105] The hybrid electrical power system 110 may also comprise a power sensor 215 as indicated in Figures 2A-B. This power sensor can be arranged to monitor frequency and / or voltage characteristics of an AC over the external power interface 130. In this case the control unit 120 can be configured to detect a time variation in frequency and / or voltage of the AC based on an output signal from the power sensor 215, and to trigger one or more automated actions in response to detecting a time variation in frequency and / or voltage which fails to meet a power stability criterion. In other words, the control unit can be configured to monitor the output signal from the power sensor 215, which can be a voltage value as function of time, and / or a frequency value for one or more phases of the incoming AC at the external power interface 130, and check if the AC characteristics are as expected. If they are not, i.e., if there is a voltage deviation or a frequency instability on one or more phases, then an automated action is triggered. The control unit 120 can also use the power sensor 215 to detect phase unbalance between two or more phases in the incoming AC at the external power interface 130. Thus, it is proposed herein to configure one or more electrical power sensors 215 in the hybrid electrical power system 1 10 of the demolition robot 100 and to use these sensors to monitor various characteristics of the incoming AC at the interface 130, such as frequency and voltage, and also phase and amplitude balance on a three-phase interface. The control unit 120 can then monitor the AC supply from the electrical power source 180 and quickly detect if there is an undesired variation in frequency and / or in amplitude of the AC, such as a drop in frequency and / or a drop in amplitude which lie outside of predetermined AC stability acceptance criteria.

[0106] The power sensor 215 preferably comprises a frequency sensor of some sort that measures the frequency of one or more phases of the incoming AC at the interface 130. The frequency sensor may comprise, e.g., a digital frequency meter configured to directly measure the frequency of the AC power, a frequency-to-voltage converter arranged to convert the frequency of the AC power into a proportional voltage, or a phase-locked loop (PLL) that lock onto the frequency of the incoming AC and provides an output signal proportional to the frequency. The power sensor 215 may be implemented as a separate component and the output signal of the power sensor 215 can then be fed to the control unit 120 for further processing. The power sensor 215 can also be integrally formed with the control unit 120, i.e., comprised in the same physical unit as the processing circuitry of the control unit 120. The power sensor determines frequency characteristics of the AC over the power interface, which is to be construed broadly to mean that the power sensor at least provides some form of data from which frequency can be inferred or determined. It is appreciated that the power sensor does not have to be configured to perform any advanced processing of the measured data.

[0107] The power sensor 215 preferably also comprises a voltage sensor that measures the amplitude characteristics of one or more phases of the incoming AC at the interface 130. Voltage sensors are generally known and will therefore not be discussed in more detail herein.

[0108] According to a preferred aspect, the one or more automated actions comprises a regulation of charging power of the auxiliary power source 140. For instance, the control unit can cease charging of the auxiliary energy source in case AC instability is detected, in order to reduce the load on the external power interface 130. The control unit can also reduce the charging current in order to reduce the load on the external power source. The charging can be resumed again once the incoming AC stabilizes.

[0109] The one or more automated actions may also comprise an adjustment of hydraulic flow delivered by a hydraulic pump 420, 460 of the demolition robot 100, possibly as function of a current pressure in the hydraulic system, in order to reduce the load on the external power interface 130. The hydraulic power is related to the total power consumption of the demolition robot 100 in a known manner, and it is approximately proportional to both the pressure and the flow. As a simple approximation, hydraulic power equals the product of hydraulic flow and hydraulic pressure in the hydraulic system. In simplified terms, the formula for hydraulic power output is Power = Q x P, where Q is the flow rate in liters per minute, and P is the pressure in bars, i.e., power is normally at least approximately proportional to both pressure and flow. To limit the electrical load on the interface 130, the control unit 120 can impose a flow limitation on the hydraulic system when pressure in the hydraulic system rises, such that the product of pressure and flow is kept below some limit. This is an advantageous way to limit power consumption since the overall capabilities of the demolition robot are often left intact. The reduction in flow just means that some tools will start to move slower when system pressure is high.

[0110] The control unit 120 can also be arranged to control hydraulic oil flow in a hydraulic circuit of the demolition robot 100 in dependence of a hydraulic pressure in the hydraulic circuit and on a maximum total power outtake of the hybrid electrical power system 110, which is given by the sum of the power available from the external electrical power source 180 and from the on-board auxiliary power source 140. This function is particularly useful if combined with the boost converter circuit or Joule thief circuit described above, since this circuit will increase the voltage of the auxiliary power source once its SOC approaches low levels, at the expense of a reduction in current output. The total power available to the demolition robot 100 is the sum of the power from the external power source 180 (drawn via the external power interface 130) and the power available from the auxiliary power source 140. This power is known to the control unit 120, either because the control unit has a power meter that provides information indicative of the available total power, or because the control unit 120 is configured to determine the total available power based on a predetermined function such as a look-up table (LUT), or because the total available power has been input manually by an operator of the demolition robot 100. Having regard to the total available power, the control unit adjusts the hydraulic flow such that the product of hydraulic flow and hydraulic pressure does not exceed the total available power. A power margin may advantageously be configured, such that the risk of consuming more power than the total available power becomes acceptable, even during transient power peaks. The AC stability acceptance criteria can be realized as fixed thresholds or ranges within which the AC frequency and / or AC voltage should lie. A variation in frequency below 5% of nominal frequency may, e.g., be acceptable. A variation in amplitude below, say 10% of nominal voltage may also be acceptable, just to give an example. The acceptance criteria can be pre-determined and / or user configurable. Some work sites may have associated acceptance criteria tailored to the specific work site, in order to optimize the different work tasks at the work sites which may be performed by different machines.

[0111] The AC stability acceptance criteria can also be time-dependent, where a short duration transient in frequency and / or voltage may be acceptable, as long as it does not persist for too long. A time-dependent acceptance criteria preferably comprises less strict acceptance criteria on short-term transient variations, and more strict acceptance criteria on more long term variations. The rationale for accepting more variation in amplitude and frequency over short time periods is that most electric hardware, such as electric motors, can handle a temporary increase in thermal load, whereas a prolonged exposure to incorrect AC can damage the hardware. When the control unit 120 detects a too large variation in AC frequency and / or AC amplitude, one or more automated actions can be triggered to mitigate the consequences of the AC instability. Possible automated actions comprise warnings to an operator, communication of data to the remote server 190 for trouble-shooting and diagnostics purposes, and also adjustments of the operations of the equipment 100 to better suit a given power source. Some aspects of the herein disclosed techniques comprise a communication channel between the control unit 120 of the demolition robot 100 and the external power source 180 which is used to power it. The automated action may then comprise exchange of messages between the demolition robot 100 and the external power source 180, such as a request for increased power sent from the demolition robot 100 to the power source 180, and / or a request for decreased load sent from the external power source 180 to the demolition robot 100.

[0112] The one or more automated actions triggered by the control unit 120 may comprise generating a warning to an operator, e.g., as a displayed message, a warning buzzer, or a warning light. The operator is then made aware of the unstable power supply, and can take action, e.g., by inactivating other machines drawing power from the same power source, or by adjusting the way the demolition robot 100 is controlled so as to draw less power from the power source 180. The warning may be issued via the display 410 at the remote control, or via some other human-machine-interface (HMI).

[0113] The one or more automated actions triggered by the control unit 120 may also comprise storing data related to an error event together with a time stamp in a digital error log file. This error log file can be retrieved and used for trouble-shooting if the demolition robot 100 suffers from malfunction. The error log file can be stored locally at the machine, and also transmitted to the remote server 190, where it can be used in the back-end system for analysis.

[0114] According to another example, the one or more automated actions triggered by the control unit 120 in response to detecting AC instability at the external power interface 130 comprises adjusting an electric load by the demolition robot 100 on the external power interface 130 in response to detecting variation of the AC over the power interface 130. Adjusting the electric load by the equipment 100 on the external power interface 130 can be done in many ways, e.g., by enforcing a hydraulic flow limitation as function of hydraulic pressure in a hydraulic system of the equipment 100 or by restricting the operations of the equipment 100 to operations that do not draw peak power.

[0115] According to some aspects, the one or more automated actions triggered by the control unit 120 in response to detecting AC instability comprises transmitting a status message to the remote server 190, which may be comprised in a back-end system of the demolition robot 100. This status message may, e.g., comprise data indicative of a detected variation in frequency and / or amplitude of the AC over the power interface. The data may also comprise information related to a phase relationship of a three- phase AC power supply. This data enables improved trouble-shooting and also simplifies maintenance and servicing decisions. Construction equipment exhibiting unexpected and / or inconsistent behavior at some work site may be diagnosed as having an unreliable power supply, which means that the construction equipment does not have to be serviced, since the experienced problems with the construction equipment are most likely due to the external power source and not to the construction equipment.

[0116] Figure 6 is a flow chart illustrating a method which summarizes at least some of the techniques discussed above. Figure 6 illustrates a computer-implemented method performed by a control unit 120 in a remote-controlled demolition robot 100 comprising a hybrid electrical power system 110. The power system 110 comprises a control unit 120, an external power interface 130 arranged to be connected to an external electrical power source 180, and an on-board auxiliary power source 140. The external power interface 130 and the auxiliary power source 140 are interconnected 230, 270 to jointly power one or more actuators 240, 280 on the construction equipment 100. The method comprises controlling S1 discharge of the auxiliary power source 140 in dependence of a state of charge, SOC, of the auxiliary power source 140, as discussed above.

[0117] According to some aspects, the method also comprises reducing S1 1 a discharge current of the auxiliary power source 140 in case a state of charge, SOC, of the auxiliary power source 140 fails to meet a first SOC acceptance criterion.

[0118] According to some aspects, the method furthermore comprises upconverting S12 a voltage of the auxiliary power source 140 in case the SOC of the auxiliary power source 140 fails to meet the first SOC acceptance criterion.

[0119] According to some aspects, the method also comprises disconnecting S13 the auxiliary power source 140 from the one or more actuators 240, 280 in case the SOC fails to meet a second SOC acceptance criterion.

[0120] Figure 7 schematically illustrates, in terms of a number of functional units, the general components of a control unit 700, such as the control unit 120 discussed above and the remote control device 500. Processing circuitry 710 is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium 730. The processing circuitry 710 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

[0121] Particularly, the processing circuitry 710 is configured to cause the demolition robot 100 to perform a set of operations, or steps, such as the methods discussed in connection to Figure 7 and the discussions above. For example, the storage medium 730 may store the set of operations, and the processing circuitry 710 may be configured to retrieve the set of operations from the storage medium 730 to cause the device to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 710 is thereby arranged to execute methods as herein disclosed. The storage medium 730 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0122] The control unit 700 may further comprise an interface 720 for communications with at least one external device. As such the interface 720 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication.

[0123] The processing circuitry 710 controls the general operation of the control unit 700, e.g., by sending data and control signals to the interface 720 and the storage medium 730, by receiving data and reports from the interface 720, and by retrieving data and instructions from the storage medium 730.

[0124] Figure 8 illustrates a computer readable medium 810 carrying a computer program comprising program code means 820 for performing the methods illustrated in Figure 7, when said program product is run on a computer. The computer readable medium and the code means may together form a computer program product 800.

Claims

CLAIMS1. Remote-controlled construction equipment (100) comprising a hybrid electrical power system (1 10), the hybrid electrical power system (110) comprising a control unit (120), an external power interface (130) arranged to be connected to an external electrical power source (180), and an on-board auxiliary power source (140), where the external power interface (130) and the auxiliary power source (140) are interconnected by a direct current, DC, bus (230), to jointly power one or more actuators (240) on the construction equipment (100), where the external power interface (130) is connected to the DC bus (230) via a rectifier (210), where the on-board auxiliary power source (140) is directly connected to the DC bus (230) in use.

2. The remote-controlled construction equipment (100) according to claim 1 , where the one or more actuators (240) on the construction equipment (100) comprises an electric motor (320) connected to the DC bus (230) via a motor driver (310).

3. The remote-controlled construction equipment (100) according to claim 1 or 2, where the rectifier (210) is adapted to limit a current drawn over the external power interface (130) from the external electrical power source (180) according to a configuration parameter of the rectifier (210).

4. The remote-controlled construction equipment (100) according to claim 3, where the control unit (120) is arranged to obtain information associated with a fuse type of the external electrical power source (180), where the control unit (120) and / or the remote control device (500) is arranged to set the configuration parameter of the rectifier (210) in accordance with the fuse type of the external electrical power source (180).

5. The remote-controlled construction equipment (100) according to any previous claim, comprising a manual decommissioning switch (340) arranged to disconnect the on-board auxiliary power source (140) from the DC bus (230) in a decommissioned mode of the hybrid electrical power system (1 10).

6. The remote-controlled construction equipment (100) according to any previous claim, where the control unit (120) comprises a first part (350) arranged tocommunicate with and / or control at least one of the one or more actuators (240) on the construction equipment (100) via a first control channel (121 ).

7. The remote-controlled construction equipment (100) according to claim 6, where control of the one or more actuators (240) on the construction equipment (100) by the first part (350) of the control unit (120), is separate from control of the transfer of electrical power to and from the DC bus (230).

8. The remote-controlled construction equipment (100) according to any previous claim, where the control unit (120) comprises a second part (360) arranged to communicate with and / or control one or more operations of the rectifier (210) via a second control channel (122).

9. The remote-controlled construction equipment (100) according to claim 8, where the second part (360) of the control unit (120) is arranged to display (390) a status message associated with a status of the hybrid electrical power system (110) on a display device of the construction equipment (100).

10. The remote-controlled construction equipment (100) according to any previous claim, where the hybrid electrical power system (1 10) comprises a battery management system, BMS, (330) arranged to communicate with and / or control one or more operations of the rectifier (210).11 . The remote-controlled construction equipment (100) according to any previous claim, where the rectifier (210) is adapted to regulate a voltage on the DC bus (230) as a voltage selected from a number of discrete voltage steps.

12. The remote-controlled construction equipment (100) according to any of claims 1 -10, where the rectifier (210) is adapted to regulate a voltage on the DC bus (230) as a continuous voltage over a predetermined voltage range.

13. Remote-controlled construction equipment (100) comprising a hybrid electrical power system (1 10), the hybrid electrical power system (110) comprising a control unit (120), an external power interface (130) arranged to be connected to an external electrical power source (180), and an on-board auxiliary power source (140), where the external power interface (130) and the auxiliary power source (140) are interconnected to jointly power one or more actuators (240, 280) on the construction equipment (100),where the control unit (120) is arranged to obtain information associated with a state of charge, SOC, of the auxiliary power source (140), and detect when the SOC fails to meet a SOC mobility acceptance criterion, where the control unit (120) is configured to inactivate at least one work-task related actuator (240, 280) on the construction equipment (100) in response to detecting that the SOC fails to meet the SOC mobility acceptance criterion, where the control unit (120) is configured to allow activation of a transport-task related actuator on the construction equipment (100) despite detecting that the SOC fails to meet the SOC mobility acceptance criterion.

14. Remote-controlled construction equipment (100) comprising a hybrid electrical power system (1 10) and a remote control device (500), the hybrid electrical power system (110) comprising a control unit (120), an external power interface (130) arranged to be connected to an external electrical power source (180), and an onboard auxiliary power source (140), where the external power interface (130) and the auxiliary power source (140) are interconnected to jointly power one or more actuators (240, 280) on the construction equipment (100), where the control unit (120) and / or the remote control device (500) is arranged to obtain information associated with a fuse type of the external electrical power source (180), where the control unit (120) and / or the remote control device (500) is arranged to configure a power limitation function of the external power interface (130) in accordance with the fuse type of the external electrical power source (180).

15. Remote-controlled construction equipment (100) comprising a hybrid electrical power system (1 10) and a remote control device (500), the hybrid electrical power system (110) comprising a control unit (120), an external power interface (130) arranged to be connected to an external electrical power source (180), and an onboard auxiliary power source (140), where the external power interface (130) and the auxiliary power source (140) are interconnected to jointly power one or more actuators (240, 280) on the construction equipment (100),the hybrid electrical power system (110) further comprising a manual decommissioning switch (340) arranged to disconnect the on-board auxiliary power source (140) from the remote-controlled construction equipment (100) in a decommissioned mode of the hybrid electrical power system (110).

16. Remote-controlled construction equipment (100) comprising a hybrid electrical power system (1 10), the hybrid electrical power system (110) comprising a control unit (120), an external power interface (130) arranged to be connected to an external electrical power source (180), and an on-board auxiliary power source (140), where the external power interface (130) and the auxiliary power source (140) are interconnected (230, 270) to jointly power one or more actuators (240, 280) on the construction equipment (100), where the control unit (120) is configured to control discharge of the auxiliary power source (140) in dependence of a state of charge, SOC, of the auxiliary power source (140).

17. The remote-controlled construction equipment (100) according to claim 16, where the auxiliary power source (140) is interconnected with the external power interface (130) via a boost converter circuit or Joule thief circuit configured to increase a voltage of the auxiliary power source (140) in case the SOC fails to meet a first SOC acceptance criterion.

18. The remote-controlled construction equipment (100) according to claim 16 or 17, where the control unit (120) is arranged to control a hydraulic oil flow in a hydraulic circuit of the remote-controlled construction equipment (100) in dependence of a hydraulic pressure in the hydraulic circuit and a maximum total power outtake of the external electrical power source (180) and the on-board auxiliary power source (140).

19. The remote-controlled construction equipment (100) according to any of claims 16-18, where the auxiliary power source (140) is interconnected with the external power interface (130) via a battery protection circuit configured to disconnect the auxiliary power source (140) from the one or more actuators (240, 280) in case the SOC fails to meet a second SOC acceptance criterion.

20. The remote-controlled construction equipment (100) according to any of claims 16-19, where the control unit (120) is configured to initiate generation of a notificationmessage to a display unit (510) of a remote control device (500) in case the SOC fails to meet a third SOC acceptance criterion.21 . The remote-controlled construction equipment (100) according to any of claims 16-20, where the external power interface (130) and the auxiliary power source (140) are interconnected (230, 270) by an alternating current, AC, bus structure.

22. The remote-controlled construction equipment (100) according to any of claims 16-20, where the external power interface (130) and the auxiliary power source (140) are interconnected (230, 270) by a direct current, DC, bus structure.

23. The remote-controlled construction equipment (100) according to any of claims 16-22, where the control unit (120) is arranged to control charging of the auxiliary power source (140) based on a present power consumption of the one or more actuators (240, 280) on the construction equipment (100).

24. The remote-controlled construction equipment (100) according to any of claims 16-23, where the hybrid electrical power system (1 10) comprises a power sensor (215) arranged to monitor frequency and / or voltage characteristics of an AC over the external power interface (130), where the control unit (120) is arranged to detect a time variation in frequency and / or voltage of the AC based on an output signal from the power sensor (215), and where the control unit (120) is arranged to trigger one or more automated actions in response to detecting a time variation in frequency and / or voltage which fails to meet a power stability criterion.

25. The remote-controlled construction equipment (100) according to claim 24, where the one or more automated actions comprises a regulation of charging power of the auxiliary power source (140).

26. The remote-controlled construction equipment (100) according to claim 24 or 25, where the one or more automated actions comprises an adjustment of hydraulic flow delivered by a hydraulic pump comprised in the one or more actuators of the remote-controlled construction equipment (100).

27. The remote-controlled construction equipment (100) according to any of claims 16-26, where the control unit (120) is configured to control charging and / or discharging of the auxiliary power source (140) in dependence of a temperature of the auxiliary power source (140).

28. The remote-controlled construction equipment (100) according to any of claims 16-27, where the auxiliary power source (140) comprises a battery pack and a capacitor arrangement, where the control unit (120) is configured to control charging and / or discharging of the battery pack and the capacitor arrangement in dependence of a state of the remote-controlled construction equipment (100).

29. A computer-implemented method performed by a control unit (120) in remote- controlled construction equipment (100) comprising a hybrid electrical power system (110), the hybrid electrical power system (110) comprising a control unit (120), an external power interface (130) arranged to be connected to an external electrical power source (180), and an on-board auxiliary power source (140), where the external power interface (130) and the auxiliary power source (140) are interconnected (230, 270) to jointly power one or more actuators (240, 280) on the construction equipment (100), the method comprising controlling (S1 ) discharge of the auxiliary power source (140) in dependence of a state of charge, SOC, of the auxiliary power source (140).

30. The method according to claim 29, comprising reducing (S11 ) a discharge current of the auxiliary power source (140) in case a state of charge, SOC, of the auxiliary power source (140) fails to meet a first SOC acceptance criterion.31 . The method according to claim 29 or 30, comprising upconverting (S12) a voltage of the auxiliary power source (140) in case the SOC of the auxiliary power source (140) fails to meet the first SOC acceptance criterion.

32. The method according to any of claims 29-31 , comprising disconnecting (S13) the auxiliary power source (140) from the one or more actuators (240, 280) in case the SOC fails to meet a second SOC acceptance criterion.

33. A computer program product comprising program code for performing, when executed by a control unit (120) comprising processing circuitry, the method of claims 29-32.

34. A non-transitory computer-readable storage medium comprising instructions, which when executed by a control unit (120) comprising processing circuitry, cause the processing circuitry to perform the method of claims 29-32.

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