Safety system, method and computer program for remotely controlled work vehicles

1. A safety system comprising:

a wireless remote control unit comprising an operator unit; and

a work vehicle comprising a vehicle unit, the work vehicle being configured to receive a first control signal from the wireless remote control unit, the first control signal being arranged to control a drive operation of the work vehicle;

wherein the operator unit is configured to transmit at least one signal carrying information relevant for positioning of the wireless remote control unit to the vehicle unit;

wherein the vehicle unit is configured to:

obtain information relating to a first position of the work vehicle,

determine a spatial relationship between the work vehicle and the wireless remote control unit based on the information relating to a first position of the work vehicle and the information relevant for positioning of the wireless remote control unit,

periodically determine if the spatial relationship meets a predetermined criterion, and

provide a second control signal to the work vehicle to control the drive operation of the work vehicle based on the periodic determinations;

wherein the work vehicle comprises an ultra-wideband, UWB, transceiver configured to transmit and receive signals comprising respective time stamps and respective unique IDs;

wherein the spatial relationship comprises a first distance between the work vehicle and the wireless remote control unit; and

wherein the predetermined criterion comprises the first distance falling within a predetermined distance interval;

wherein the vehicle unit is configured to determine the first distance using two-way ranging time of flight based on a time stamp based on the information relating to a position of the work vehicle that is time stamped at an initial time of the two-way ranging and a time stamp based on a received signal that is time stamped at a finishing time of the two-way ranging.

2. The safety system according to claim 1 , wherein the vehicle unit further comprises a processing element, wherein the processing element is communicatively connected to the drive operation, and wherein the processing element is arranged to control the drive operation of the work vehicle by providing the second control signal.

3. The safety system according to claim 2 , wherein the processing element further comprises processing circuitry arranged to receive the information relating to a first position of the work vehicle and the information relevant for positioning of the wireless remote control unit, and wherein the processing circuitry is further arranged to determine said spatial relationship and generate the second signal based on whether the spatial relationship meets the predetermined criterion.

4. The safety system according to claim 1 , wherein the second control signal is arranged to stop movement of the work vehicle if the work vehicle enters the predetermined distance interval.

5. The safety system according to claim 1 , characterized in that the vehicle unit comprises a first transceiver and the operator unit comprises a second transceiver, wherein the first transceiver is arranged to transmit an initiation signal at said initial time to the second transceiver, and wherein second transceiver is arranged to receive the initiation signal and transmit a response signal to the first transceiver, the response signal comprising said time stamp for the finishing time.

6. The safety system according to claim 1 , wherein the information relevant for positioning of the work vehicle comprises information relating to a second position of the work vehicle, wherein the spatial relationship further relates to a second distance between the work vehicle and the wireless remote control unit based on the second position, and wherein the predetermined criterion comprises the second distance falling within a second predetermined distance interval.

7. The safety system according to claim 1 , wherein the vehicle unit and the wireless remote control unit each comprises direction detection means arranged to determine a direction of the work vehicle and the wireless remote control unit, respectively, wherein the vehicle unit is further arranged to determine a relative direction between the determined directions of the work vehicle and the wireless remote control unit, and wherein the vehicle unit is arranged to stop the work vehicle based on a predetermined relative direction criterion.

8. The safety system according to claim 1 , wherein the operator unit comprises a first orientation sensor, wherein the first orientation sensor is arranged to determine an acceleration or a change in orientation of the wireless remote control unit, and wherein the vehicle unit is arranged to stop the work vehicle based on the determined acceleration and/or change in orientation meeting at least one predetermined criterion.

9. The safety system according to claim 8 , wherein the vehicle unit comprises a second orientation sensor arranged to provide the vehicle unit with information relating to roll, pitch and heading of the work vehicle, wherein the vehicle unit is further arranged to stop the work vehicle based on the information relating to roll, pitch and heading of the work vehicle meeting at least one predetermined criterion.

10. The safety system according to claim 1 , wherein the vehicle unit comprises a temperature sensor, wherein the temperature sensor is arranged to provide the vehicle unit with information relating to a temperature of the work vehicle, wherein the vehicle unit is further arranged to provide at least one second control signal based on the information relating to said temperature of the work vehicle meeting a predetermined criterion.

11. A method performed in a safety system for a remotely operated work vehicle, the work vehicle being arranged to receive a first control signal from a wireless remote control unit, the first control signal being arranged to control a drive operation of the work vehicle, wherein the safety system comprises the wireless remote control comprising an operator unit and the work vehicle comprising a vehicle unit, the work vehicle further comprising an ultra-wideband, UWB, transceiver arranged to transmit and receive signals comprising a unique ID and a time stamp, wherein the method comprises:

obtaining information relating to a first position of the work vehicle, the information relating to a first position of the work vehicle comprising a first time stamp of an initial time;

transmitting, at the initial time, at least one signal carrying information relevant for positioning of the wireless remote control unit to the vehicle unit, the information relevant for positioning comprising a first unique ID and the first time stamp;

determining, based on the first unique ID and using two-way ranging time of flight, a spatial relationship between the work vehicle and the wireless remote control unit based on the information relating to a first position of the work vehicle and the information relevant for positioning of the wireless remote control unit, wherein the two-way ranging time of flight is based on the first time stamp and a second time stamp at a finishing time of the two-way ranging;

periodically determining if the spatial relationship meets a predetermined criterion; and

providing a second control signal to the work vehicle to control the drive operation of the work vehicle based on the periodic determination.

12. The method according to claim 11 , wherein determining the spatial relationship further comprises

determining a first and a second distance between the work vehicle and the wireless remote control unit; wherein periodically determining if the spatial relationship meets a predetermined criterion further comprises

for each of the first and second distances, determining if at least one of the first and second distances falls within a predetermined distance interval; and wherein providing a second control signal to the work vehicle further comprises

arranging the at least one second control signal to stop the work vehicle if at least one of the first and second distances fall within the predetermined distance interval and fall within a second predetermined distance interval.

13. The method according to claim 11 , wherein the method further comprises:

obtaining information relating to roll, pitch and heading of the work vehicle; and

arranging the at least one second control signal to stop the work vehicle if at least one of the roll, pitch and heading meets a predetermined criterion.

14. A non-transitory computer readable medium comprising computer program code which, when executed, causes a safety system to carry out the method according to claim 11 .